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HIGH VOLTAGE AND X-RADIATION PROTECTIONA potential source of x-rays is the picture tube, if the highvoltage (HV) is out of specification. When the HV is operatingproperly, there is no x-radiation. For the CA chassis family,the HV has no adjustments. A HV shutdown circuit is used toprevent excessive HV and x-ray emissions.
THEORY OF OPERATION (SHUTDOWN CIRCUIT)This circuit basically monitors the sweep pulse voltage de-rived from the sweep transformer TX3204 pins 5 & 6. Thisvoltage is rectified, and applied to a 12V zener diode ZDX3004.When the HV reaches its maximum allowed ,value (see draw-ing) the zener diode conducts, the voltage on pin 29 of thevideo processor (ICX2200) increases until it reaches the thresh-old voltage of 3.5 VDC, and shuts down the TV. If the shut-down circuit has operated, the microcontroller will preventthe TV from being turned on again, without first having tounplug the AC cord to reset the microcontroller.
TIP: Make a momentary short between the OUTPUT and GNDof the IC6002 (RESET CIRCUIT) this will reset the microcontrollerIC6000. Apply signal through the video generator or tune theTV color receiver to crosshatch pattern. Connect an accurateHV meter between the picture tube anode and chassis ground.Access Video Menu and adjust Brightness and Contrast con-trols for minimum screen luminance. Wait until, the VideoMenu or display disappear. Read HV meter.
SAFETY CIRCUIT TEST PROCEDUREEquipment required:
a) Video Generator.
b) HV DC meter (0 to 40 KV, high Z).
c) External variable power supply (0V to 200 VDC @ 5Ampsminimum).
d) 1 Giga ohm, 5%, 2W film resistor.
Before turning the TV on, connect the HV meter�s negativeprobe (-) to ground (DAG ground recommended) and the posi-tive probe (+) in the anode of the CRT. Connect a 1 Giga Ohmresistor in parallel with the HV meter. Then connect the exter-nal power supply�s negative output (-) to chassis ground, thatis, the negative lead of B+ filter capacitor, CX3420. Turn onthe TV. Apply a video signal or tune the TV to a raster pattern.Adjust the G2 potentiometer for minimum, and set the bright-ness and contrast levels to minimum. Now adjust the outputvoltage of the external power supply to 124 VDC for CA25V/27V or 130 VDC for CA32V/36V. Then start increasing thevoltage on the external power supply until the TV shuts down,and read the HV on the meter just before the voltage startsdropping.
Note: The external power supply may require a diode forblocking voltage from the chassis power supply tothe external power supply. The diode should beconnected between the positive output of the externalpower and B+ of the chassis. The cathode should befacing the B+ of the chassis. The recommended diodeis Part No. 103-00339-04A (400 V of VRRM @ 3Amps of average rectified forward current).
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CA-ii
CA Chassis Safety Guidelines
CA-iii
Preface
This manual has been designed as a supplement to the CM-151 CA/CB training manual (923-3351TRM).It provides circuit descriptions as well as troubleshooting flowcharts for both CA and CB chassis. Eachdescription includes schematic diagrams of the particular section(s) being discussed. These inclusionsrepresent a change from some recent training manuals. Moreover, this manual is divided into two distinctsections, respectively, for CA and CB chassis. Such an arrangement should prevent confusion between thetwo.
Many servicers prefer to use their training manuals in conjunction with the corresponding service manuals.As such, the schematics contained in this training supplement were drawn to be fairly generic. However, asa concession to those who desire a quick reference, tables that include part numbers of major componentshave been supplied in each applicable circuit description. Note that these part numbers should only beapplied to those sets which fall under component level repair warranty. (32� and 36� sets have a modulereplacement warranty.) Hence, when a table refers to �all models�, it can only apply with certainty to allcomponent level repairable modules. Likewise, in the troubleshooting section, flowcharts will often instructthe repair technician to replace a certain component under a particular situation. Again, such instructionconcerns component level repair sets. Still, the flowcharts provide useful information for diagnosing aproblem on component level warranty modules and replacement warranty modules alike.
Frequently, the tables refer the reader to the service manual for particular models associated with givenparts, particularly with regard to the CA chassis. This is because at the time this manual was produced,there were 81 variants of the CA chassis in the field. In any case, parts referencing is really beyond thescope of a training manual. Furthermore, it is a good idea when looking up part numbers to refer to up-to-date service information. Generally speaking, training in circuit theory and operation does not change whenpart numbers do.
Finally, be sure to take special note of the safety information supplied in this manual. General safety infor-mation is provided for both chassis on the reverse side of the front cover. High voltage protection instruc-tion for the CA chassis is located on the page following the general safety page and for the CB chassis at thestart of the second section of this manual.
CA-iv
Table of Contents
Section 1General Safety Guidelines ................................................................................... CA-iCA Chassis Safety Guidelines ................................................................................... CA-iiPreface ................................................................................... CA-iiiThis Table of Contents ................................................................................... CA-ivCA Circuit Descriptions
Power Supply ................................................................................... CA-1Microprocessor Control ................................................................................... CA-5IF Receiver ................................................................................... CA-9Video Processing ................................................................................... CA-11Deflection Control ................................................................................... CA-17Audio Development ................................................................................... CA-22
CA Troubleshooting ................................................................................... CA-27
Section 2CB Chassis Safety Guidelines ................................................................................... CB-iCB Circuit Descriptions
Power Supply ................................................................................... CB-1Microprocessor Control ................................................................................... CB-5IF Receiver ................................................................................... CB-9A/V Switching ................................................................................... CB-12Video Processing ................................................................................... CB-16Deflection Control ................................................................................... CB-22Audio Development ................................................................................... CB-27
CB Troubleshooting ................................................................................... CB-30
CA-1
Power Supply
Introduction
The CA chassis is a cold ground chassis deriving its power from a switch-mode, flyback type, powersupply. It features indirect B+ regulation, over-current protection (OCP), software controlled degaussing,necessities for Energy Star compliance, and provision for future universal power input (85VAC - 265VAC).
The switch-mode power supply, or SMPS, converts AC line power to the various DC voltages required bythe receiver. Note that there is no switch to activate or deactivate the SMPS. It operates as soon as ACline power is present. Input power demands can reach a maximum of 130 watts on 25 and 27 inch sets and145 and 150 watts on 32 and 36 inch sets respectively.
Switch-Mode Power Supply Primary Side
The receiver is protected from AC line surges by FX3401, a 4A, 250V fast-blow fuse. The AC operatingrange is between 90Vrms and 135Vrms. AC is first filtered by LX3401 and CX3402. It is then rectifiedusing a diode bridge (package DX3400 on 32"/36", discrete components DX3401 through 3404 on 25"/27"). CX3407 smoothes out the resulting DC voltage. It is from this voltage (called VDC or raw B+) thatthe heart of the SMPS, the Switch-Mode Regulator, is run. Raw B+ can run anywhere from +127VDC to+191VDC.
DX3402
DX3403
DX3401
DX3404RX3401
CX3406
C3403
CX3407
CX3404
CX3405
CX3402
B+ VDC
LX3401
CX3401EX3401
RX3400
CX3400
FX3401
3R8
DX3400
To DegaussingCircuit
<<Figure CA-1>>
Primary components of the Switch-Mode Regulator circuit include the switching transistor, QX3401; theregulator IC, ICX3400; and the chopper transformer, TX3401. The actual chopper used will depend onthe size of the set. This transformer isolates the rectifier and regulator sections, which use hot ground, fromthe rest of the CA chassis, which uses cold ground.
When line power is introduced to the set, raw B+ is supplied to pin 18 of the chopper (switch-modetransformer). At the same time a small amount of raw B+ is drawn through RX3404 into pin 2 ofICX3400. This voltage triggers the switching of a transistor internal to the regulator IC. Once this happens,current begins to alternate between flow and rest in the raw B+ winding (pins 18 and 11) of the switch-mode transformer. Alternation will occur at a frequency of approximately 25 KHz when the set is in stand-by, and near 50KHz when the set is powered up. Because of the transformer action, base drive to pin 2 ofICX3400 is from this time forward maintained by another winding on the chopper (pins 13 and 15) throughCX3416.
CA-2
CA CIRCUIT DESCRIPTIONS
<<Figure CA-2>>
Another winding from the chopper (pins 13 and 16) provides feedback to the regulation loop in ICX3400.The AC from this winding is half-wave rectified by DX3408 to supply a negative voltage to pin 1 of theregulator IC. ICX3400 is designed in such a way that it will adjust both its oscillating frequency and dutycycle to maintain -41 volts DC on pin 1. Thus as changing power demands are reflected in the choppertransformer, feedback to ICX3400 triggers a corresponding change in the regulated supply.
ICX3400
TX3401
QX3401
CX3410
RX3406
DX3406
CX3409CX3408
RX3404
RX3408RX3407
RX3403
B+ VDC
CX3411
DX3407
CX3412 CX3413
RX3409DX3408
C3418
CX3416
LX3410
B+ VDC
RX3405 CX3415
RX3410PROV
C3414PROV
RX3411PROV
DX3409PROV
B+ VDC
16
ToRegulatedB+
To+18 VSB
5
7
8
4
115
13
11
18
54321
Q-Switching
Q-Reg
Q-Limiter
DZRegR-ShuntR-Bias
R-Div2R-Div1
5
4
3
2
1
R-AntiSat
223-00028ICX3400
<<Figure CA-3>>
QX3401 serves as the Over-Current Protection (OCP) switch. If the current sensing resistor, RX3403,passes too much current to pin 4 of ICX3400 (the emitter of the internal switching transistor), the resulting
CA-3
Power Supplyvoltage at the base of QX3401 will switch that transistor on, shunting the regulator IC�s base drive toground. Such an action kills the regulator�s oscillation, thereby eliminating power generation.
Several capacitors, CX3408, CX3409, CX3410, and CX3412, are used in the SMPS to reduce EMI(electro-magnetic interference). Additionally, RX3405 and CX3415 serve as a snubber circuit, to reducepeak voltage on the collector (pin 3) of ICX3400�s switching transistor.
Switch-Mode Power Supply Secondary Side
The two windings on the secondary side of the chopper transformer generate the regulated B+ (or simplyB+) which, depending on the size of the television, will be either +124 volts DC or +130 volts DC, and the+18 volts DC. Both are present when AC line voltage is supplied to the SMPS. Hence these voltages maybe considered Stand-By (SB). The B+ supplies necessary power to the horizontal sweep and the horizon-tal output sections. It is filtered and rectified using LX3403, C3419, and D3410, and it can be measuredacross CX3420. Note that the B+ line does not have a fuse. The OCP circuit mentioned above serves toshutdown the power supply if too much current is drawn through the regulated B+ circuit.
TX3401
LX3403
LX3404 DX3411
D3410
CX3424CX3420
C3421
C3419 B+
+18 VSB
RX3428
ZDX3401 C3460
+15 VSW
R3427
R3423
C3425
OUTIN1
2
3
ICX3402
C3426
+5 VSBQ3406PROVFX3402
W3402
R3422M
PROV
L3407
R3424PROV
D3414PROV
Q3402
R3418
R3414Q3404
R3412M
Q3405PROV
R3425MPROV
R3426MPROV
W3401
L3405
CX3430C3428PROVC3429
RX3417OUT IN1
2
3
ICX3401
+9 VSW
4
1
7
5
8
Power ControlPulse fromPin 32, IC6000
+18VSW
+18VAUDIO
+5VTUNER
<<Figure CA-4>>
On the other hand, the +18 volts DC (or +18 VSB) is fused by FX3402. Rectification and filtering of the+18 VSB is accomplished by an arrangement similar to that of the B+. The resulting +18 volts DC may bemeasured across CX3424. This voltage is further broken down to provide power to various circuitsdescribed below.
CA-4
CA CIRCUIT DESCRIPTIONSICX3402 regulates from the +18 VSB to provide +5 VSB. The +5 VSB powers the microprocessor,IC6000, and the tuner, TU6000. Additionally, part of the power from the +18 VSB supplies +18 volts tothe audio circuitry (+18 AUD). The remainder of the +18VSB power is used when the set is powered up.This powered up voltage is typically referred to as a switched voltage (VSW). The +18 VSW powers thehorizontal drive amplifier. That same +18 VSW is also regulated through ICX3401 to produce a +9 VSW.This +9 volts powers the video signal processor, ICX2200, and, in stereo sets, IC1400. Finally, a +15VSW is generated from the +18 VSW using RX3428, ZDX3401, and C3460. The +15 volt supplypowers the ABL video and the variable audio output circuits.
These switched voltages turn on given a DC level from pin 32 of IC6000. This signal will of course comeon when triggered by the power on key from the keyboard or the IR detector, IR6000. The DC level at pin32 should be near +4.8 volts DC. This will drop across R3418 and switch the base of Q3402. As thistransistor turns on, it drives Q3404 into saturation and activates the switched voltages.
Degaussing Control
Degaussing is accomplished via software in the CA chassis. At turn on, pin 33 of IC6000 generates a +4.8volt DC level. After dropping through R3419, this DC switches on Q3403 to allow current flow throughthe degaussing relay, KX3401. With the relay now turned on, filtered AC line current travels into thedegaussing coil passing through the thermistor, THX3415. 760 milliseconds after power-up, the micropro-cessor sets the voltage to zero, and the relay opens cutting off AC to the coil.
KX3401
DX3405
Q3403
THX3415
+18 VSW
R34192
1
FilteredAC Line
DegaussingControl, Pin 33,IC6000
3T8 -- ToDegaussingCoil
<<Figure CA-5>>
CA-5
Microprocessor Control
Introduction
The CA chassis employs IC6000 as its microcontroller. All end user and servicer controls are accessedusing this IC. While most of its functions will be described in terms of how they are used by other devices inthe receiver, a number of facts concerning the microprocessor and its input devices will now be presented.
The microprocessor�s job is to communicate control instructions and feedback information to and fromvarious other processors and input devices in the set. These include the video, audio, PiP, audio & videoswitch ICs, the tuner, the EEPROM, the keyboard and IR detector, and the reset IC. Some of these use adirect connection via either switch, variable pulse, or DC level for communication. Others rely on the I2Cbus, also known as serial clock and data bus. IC6000 provides 2 sets of clock and data lines. The first setis pins 37 and 39, and the second is on pins 36 and 38. The EEPROM and the factory setup connector,4G9, are the only devices which receive clock and data pulses from the first set.
Input Devices
The IR detector demodulates pulses from the 40 kHz modulated carrier and sends the pulses to pin 15 ofthe microprocessor. There a special algorithm interprets the pulses as the various commands they represent.The keyboard is only slightly more complicated in its operation external to IC6000. It works by varyingvoltage on only two input pins (7 and 8) using resistor networks. A/D converters inside the micro interpretthe different voltages. Because voltage detection is used rather than active keyboard scanning, keyboardradiation is not a problem, but maintaining a +5VSB to within ±4% is critical.
R6018
R6017M
R6020M
R6019M
R6022MR6025M
R6021MR6023MR6024M
+5VSBF
R6015
R6016
R6069M
R6070M
C6042MC6043M
Pin 7
Pin 8
1
2
3
4
5
+5VSBF
L6005
C6036MR6029MC6035PROV
L6004
Pin 15
C6004
R6028
C6092M
C6003M
R6027
2K6
3
2
1
IR6000
GND
VS
VOUT
EXTERNALKEYBOARD
Keyboard& IR Input toIC6000
SW1ON/OFF
SW2CH-UP
SW3CH-DN
SW4VOL-UP
SW5VOL-DN
SW6MENU
<<Figure CA-6>>
CA-6
CA CIRCUIT DESCRIPTIONSFor those CA chassis that have the keyboard and IR detector built onto the module, the schematics areincluded. Keep in mind, however, that many of the various CA chassis have a keyboard and IR module thatis separate from the main board.
Microcontroller
VCC is provided to pin 27 of the microprocessor from the +5VSBF supply. While this voltage is relativelylow, IC6000 is fairly demanding in terms of current. This same voltage also powers the keyboard and IRdetector. Additionally, the +5VSBF is used as analog VCC and enters the micro at pin 18.
IC6002 serves as a reset IC for the main microprocessor. Note that it comes in a transistor type package.It accurately resets the micro when SB voltage is detected. Pin 30 is the reset signal input for IC6000. Themicro enters reset state after detecting a low on pin 30 of 2µS or more.
When the micro receives a power on signal from either the keyboard or the remote, the degaussing controlpin 33 turns on the degaussing circuit for 760ms. At the same time a constant voltage level from pin 32turns on the switched voltages in the power supply.
<<Figure CA-6>>
Horizontal and vertical synchronization pulses are fed into pins 1 and 2. These provide the microprocessorthe current sweep location of the beam, which is necessary to correctly interrupt main video for various
C6012MC6013
L6001
+5VSB +5VSBF
C6017
R6037M
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
36
26 27
28
29
30
31
32
33
34
35
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52HSYNC
VSYNC
AFC
FM_SD
NC
SYNC
A/D_KEY2
A/D_KEY1
NC
Y/C-SENSE
PiP_BRT
NC
CRT-PROT
MUTE
REMOTE
NC
NC
AVCC
HLF
RVCO
VHOLD
CVIN
CNVSS
XIN
XOUT
VSS
R
G
B
FB
VERT-SIZE
HORZ-SIZE
VOL
NC
AUD-SWITCH
PiPSWITCH1
AUX_SW1
NC
H/T
SCL1
SCL2
SDA1
SDA2
IDENT
RADIO/TV
DEG-CTL
POWER
CHASSIS-ID
RESET
OSC-OUT
OSC-IN
VCC
IC6000
VCC
GND
OUT
IC6002
C6016 C6056M D6001
CRY6002PROV
L6002
R6060MR6035MC6015M
C6014M
R6059M
CRY6001
R6034M
C6010M C6011M
C6008MPROVR6080
R6033MC6009
R6032M
C6007M
R6031M
PROV
C6006
C6005M
C6098
R6030L6007
+5VSBF
C6037
To IR6000
R6026
C6040M
C6092M
C6090M
C6093M
To Keyboard
+5VSBF
C6062M
R6001M
R6005M
R6012M
R6058M
D6002
R6053M
C6061M
C6079M
R6061M
C6058M
R6090M
Q6001
Q6002C6068M
R6008MR6002M
R6004MR6003M C6001M
C6024MPROV C6025M
PROV C6033MPROV
C6023M
R6082M
C6067MR6084M
C6099
Q6003C6066PROV
C6064MR6083M
R6040M
R6081M
C6057M
C6041M
C6094MPROV
R6036M
C6018M
C6046M
C6045M
C6051M
C6052M
C6053M
C6095M C6038MC6055M
FLYBACK
V-RAMPV-DRIVE
AFC
PiP-BAT
SYNC
Y/C-SENSE
CRT-PROTECTORMUTE
PWR-CTLDEG-CTL
AUX-SWITCH1PiP-SWITCH1AUD-SWITCH
VOL-CTRLHORZ-SIZEVERT-SIZE
HALFTONEFASTBLANK
B+UPG+UPR+UP
COMPOSITEVIDEO IN
EEPROM& FactorySetup Ckt
CA-7
Microprocessor Controltypes of on-screen display (OSD). Neither sync pulses come directly from the video processor where theyare first produced. Horizontal sync is actually fed back from the sweep transformer on the flyback pulseline. Vertical ramp signals feed the base of Q6002. Sync is produced on the collector and fed to thevertical amplifier and through R6006M to the V-Sync pin of the micro. OSD or CC (closed captions) aresent as processed RGB (red, green, & blue) from pins 50, 51, and 52. At those times it is necessary toblank out main video, a fast-blank (FB) pulse is sent to the video processor from pin 49 along with theprocessed RGB. An exception to this occurs when PiP is displayed. Under that circumstance, the fast-blanking pulse without RGB is sent to the video processor.
Some CA chassis feature a halftone function that dims video surrounding OSD. This halftone circuit isdescribed in the video section, but is controlled by a DC level from pin 40.
Closed captioning display is accomplished in the microprocessor by use of the composite video into pin 22.Here a data slicer extracts the caption information and outputs it to the RGB pins when captioning is re-quested by the user. Note that when OSD needs to be on the screen, such as after a channel change orduring a volume change, the OSD will have priority, and CC will mute. IC6000 also gains synchronyinformation from the composite video stream.
Pin 6 is a signal detection pin. When the tuner sends a bona-fide signal to the video processor, it separatesthe horizontal sync signal from the IF and sends it to this portion of the microprocessor. It can then be usedto determine if a certain channel is carrying an active broadcast.
Automatic frequency correction (AFC) is sent to the microprocessor via pin 3. The DC level on pin 3 tellsthe microprocessor if it needs to communicate an adjustment to the tuner to allow for clearer channelreception. The ideal voltage level here should be approximately +2.5 volts.
IC6000 provides CRT-protection for the set through pin 13. Operation of this shutdown depends on a DClevel from the CRT protection circuit off the vertical amplifier circuit. Should the vertical IC2100 fail, theDC level will no longer be present. In this situation, the CRT-protection latch will shut the receiver downthree seconds after detecting the failure. This circuit will prevent the CRT from burning a horizontal phos-phor line in the center of the screen or, worse yet, cutting the yoke end of the tube off completely.
The remainder of the input and output pins of IC6000 are adequately described in other sections of thismanual. Refer to the video, audio, and deflection sections of the CA chassis for these descriptions.
IC Location Part # NotesIC6000 221-01384-01
221-01384-02 Refer to Service Manual221-01386-01 for Corresponding Model 221-01387-01
IC6001 221-00745-04 All ModelsIC6002 221-01177A All Models
<<Table CA-1>>
CA-8
CA CIRCUIT DESCRIPTIONS
Memory
The EEPROM, IC6001, is a small but vital part of the CA receiver. This 512 byte memory chip is respon-sible for storing servicer adjustments, channel information, and user settings, even when power is removedfrom the set. This information is transferred on the clock and data lines from the micro into pins 5 and 6.The EEPROM is powered by the +5VSBF source at pin 8.
1
2
3
4 5
6
7
8
IC6001
R6049
R6050M
+5VSBF
L6003
C6020 C6021M
1
2
3
4
5
+5VSBF
R6072R6039M
C6019M
R6046M
R6045M
R6047M
R6048M
C6047MC6048MC6049MC6050M
IDENTDATA2DATA1CLOCK2CLOCK1
R6041R6042MR6043R6044M
CLOCK2DATA2
(IC6000)3536373839
Clock & Datafor Tuner, Videoand Audio
4G9
<<Figure CA-7>>
CA-9
IF Receiver
Tuner
Cable or off-air signals are received into the television by way of the antenna jack of the tuner, TU6000.The input and output impedance of this device is 75 ohms. It provides for 181 channels (including cable).It uses +33V for tuning, +5VTune as tuner B+, +4.3V for AGC, and on some chassis +9VSW.
As with standard varactor tuners, varying voltage across an internal varactor results in a different internalresonant frequency, whereby tuning of the various channels is achieved. Control of this process is accom-plished through the I2C (serial clock and data) lines attached to pins 4 and 5 of TU6000. These transfercontrol data to and from IC6000.
AGC (automatic gain control) voltage is applied to pin 1 of the tuner from pin 3 of ICX2200. This DCvoltage varies in response to signal strength from the tuner so as to avoid signal distortion not only from lowsignal levels, but also from signals strong enough to otherwise cause clipping distortion. AGC voltage willalter the signal level accordingly.
<<Figure CA-8>>
IF Processor
Tuner IF (intermediate frequency) comes from pin 11 of the tuner. This is filtered and amplified (seeQ1200, U1200, and surrounding circuitry) before it is fed into pins 7 and 8 of ICX2200, the IF/videoprocessor (sometimes called the Jungle chip). IF consists of PIF (Picture IF), SIF (Sound IF), and CIF(Chroma IF).
+33V
+5VTune
+9VSW
ZD6001 C6032 C6031M
C6030 C6029M
L6000
CX6027 C6026M
TP6006 TP6005 IF
TP6010
C6090PROV
C6070
PROV
Clock2
Data2
TP6004
C6028
J6000M **
RF-AGC
** ONLY FOR 175-2771 TUNER
OMIT FOR 175-2771 TUNER
From Pins36 and 38,IC6000
11
10
9
8
7
6
5
4
3
2
1
TU6000
CA-10
CA CIRCUIT DESCRIPTIONS
<<Figure CA-9>>
ICX2200 powers its IF section using +9VPIF (pin 9) and +9VSIF (pin 48). The IC�s main VCC is a+9VF supply to pin 46. IF signal continues from pin 47 at nearly 2Vp-p to an FM trap where SIF isseparated from PIF. SIF reenters ICX2200 at pin 52, the limiter. From this, composite audio is developedand transmitted from pin 2 of the video processor to the audio circuitry. The remaining PIF passes throughQ1202 for de-amplification to 1Vp-p. The resulting signal, denoted TVIN, is passed to both the Jungle ICat pin 37 and pin 5 of IC2902 (refer to the jack-pack and switching section below).
AFT (automatic fine tuning) is also derived from the video processor at pin 44. This signal feeds the micro-processor, IC6000, to generate minute tuning adjustments so as to maintain optimum channel quality.
Part Location Part # NotesTU6000 175-02721 Refer to Service Manual
175-02771 for Corresponding ModelsICX2200 221-01165 All Models
<<Table CA-2>>
C
1
2
3
4
5
6
7
8
9 8
49
50
51
52
53
54
55
56NC NC
SND-OUT
RF-AGC
SIF
AGC-FIL
PIFGND
PIF-IN
PIF-IN
PIF-VCC SIF-VC
PIFTANK
PIFTANK
SIFGND
LIMITER
AUDIN
EXT-AUD
DE-EMPH
47TV/DET
46
10
11
LOOPFIL
APCFIL VCC
ICX2200 TP1248 TP1245
C1214
C1213M
TP1201
+9VSW
L1203L1200
C1215M
+9VSIF
C1216
+9VPIF
R1225 R1200M C1200M
R1201M
3
2
1
L1202
R1210M
C1205M
C1206
R1231M
TP1200
1
2
4
5
3
U1200
R1211M
C1204M
R1209M
+9VPIF
R1206M
Q1200
L1201C1202M
R1205M
R1204M
R1203M
C1201M
R1202M
IF
R1207M
R1208M C1203M
+9VSW
R1212MC1208M
C1207U1201
R1214M
C1217M
C1218M
L1204
R1215M
+9VPIF
C1209M C1210
C1212 R1213M
C1211M
Q1201
TP1202
R1216M
R1217M
R1218M
U1202
L1205
R1219M
Q1202
C2237M
R1221M
R1220M
TVIN
3
2
1
L1206
+9VSIF
C1219M
+9VSW +9VF
L1207
C1220M C1221MC1222
6
4
AGCPin 1,TU6000
CompositeAudio
4
CA-11
Video Processing
Introduction
ICX2200 has numerous duties involved in television image and sound production. As mentioned above, itprocesses sound and video IF. Additionally, it prepares NTSC video utilizing separated chroma, luma, andOSD from IC6000. Accounting for controlled preference information from the micro such as brightness,tint, sharpness, contrast, etc... the �Jungle� chip then produces this video signal as RGB which is amplifiedand sent to the picture tube. Finally, the video processor generates the very drive signals that cause thedeflection circuitry to operate and produce high voltage as well as picture.
A/V Switching
At this point, because of its interaction with the video processor, an explanation of the jack-pack switchingsection is expedient. Depending on the extra features a CA receiver has (S-VHS Video or Y/C, PiP), thechassis will have two switching ICs, IC2901 and IC2902. IC2902 is the PiP switching IC. The first
12
11
10
9
8
7
6
5
4
3
2
1
CH-2
CH-1
IC2901
12
11
10
9
8
7
6
5
4
3
2
1
CH-2
CH-1
IC2902
C2908
R2901M
R2915M
C2911 C2904
+9VSW
R2919M
R2918M
R2922M
Q2902
C2915M
C2913
C2910
C2912M
C2916
C2917M
C2914
R2920M
R2921M
C2906
C2900
C2909
W2903
J2902M
R2902M
ZD2901
R2923M
R2907
C2902M
C2918L2901
C2903MR2905M
C2918
R2917M
ZD2903
R2914
R2916
ZD2902
R2908
R2910M R2911
R2909
C2907M
R2912
Ext-LExt-RVM Out-LVM Out-R
CMChroma-CombAux Switch1Ext Video
Y/C SensePiP Switch1TVINVIN PiP
J1External
LeftExternal
RightVariable Monitor
Out - LeftVariable Monitor
Out- RightVideo-In S-VHS
12 11 9 8 7 6 5 124 310
<<Figure CA-10>>
CA-12
CA CIRCUIT DESCRIPTIONSswitching channel of this IC switches the PiP between external and internal video sources based on the PiPSwitch1 signal (pin 4, IC2902) from the microprocessor. The internal video signal, denoted TVIN, is thesame signal as the one entering pin 37 of ICX2200. Whichever signal is selected is sent as VIN PiP to thePiP module through pin 10 of the PIPA1 connector. The second switching channel of IC2902 allowsselection between composite video input and S-Video input. While normally it defaults to composite video,its switching action is based on the presence of S-Video. The output of this switch feeds the external side ofthe PiP switch.
IC2901 is referred to as the main switching IC. Both switching channels of IC2901 are controlled by theAuxSwitch1 input from the microprocessor. It is tempting at first glance to assume that this IC switchesbetween external and internal video sources. However, ICX2200 actually handles that process internally.Rather, IC2901 switches the between the external source to be viewed (composite or S-Video) on switch-ing channel 2. The output from this channel goes to pin 39 of ICX2200, the external video input. Channel1 switches between the internally separated chroma signal and the S-Video chroma signal, and feed itsoutput back to pin 45. See below for a further description of video separation.
Video Development
For video processing, ICX2200 will switch between tuner IF, which as discussed above enters the IC at pin37, or an external video source, which enters the Jungle chip at pin 39. Switching between these will bedirected by the microprocessor via the I2C bus entering ICX2200 on pins 27 and 28. The selected signal isemitted from the switched video out pin (41) as composite video. This signal is sent to the microprocessorand the glass comb-filter, DL2200.
The purpose of the comb-filter is to separate chroma from luma. Its superiority to conventional filtering andseparation schemes is that it reduces cross talk between chroma and high-frequency luma. Historically, setswithout this feature were prone to have rainbow effects on objects whose luminance frequency approachedthe 3.58 MHz color subcarrier. (Note that this frequency is established by CR2201, the color crystal in CAchassis.) The result of the comb-filter�s operation is that cross color distortion is minimized for much morehighly detailed objects.
Composite video enters the comb-filter on pin 2. Luma is produced on pin 5 and is fed to pin 43. A3.58MHz trap (C2229M, L2201, & R2245M) removes any residue chroma. Separated chroma exits thecomb-filter at pin 3. In sets that utilize IC2901 for jack-pack switching purposes, chroma from the comb-filter is sent to pin 5 and exits at pin 8. This signal is then denoted by CM, and is passed back to the videoprocessor via pin 45. (In sets that do not use IC2901, chroma passes directly to pin 45.) A band-passfilter (C2232M, R2253M, & L2202) eliminates any remaining luma.
Once inside the Jungle IC, luma is processed with numerous factors including contrast and brightness.Brightness and contrast information from the beam current passes into pins 36 and 38 from the circuitryconsisting of Q2204, 2205, and 2209. ICX2200 responds to this information by limiting (when necessary)contrast and brightness to the RGB outputs. Basically, the ABL responds to current from pin 8 of thesweep transformer, TX3204. D2204, R2235, and C2220 make this signal positive. It is then inverted byQ2205 and smoothed as it passes to Q2204. As beam current approaches 1.5 mA (1.3 mA on 25�, 0.9mA on 19�/20�) Q2209 starts to turn on and shunts excess current to ground. In addition to controlling the
CA-13
Video ProcessingRGB output, this circuit helps to prevent blooming. Excessive current draw in the picture tube will lowervoltage and hence decrease beam acceleration. This results in an increase of the sweep. Without ABL, theblooming effect is usually seen when very bright images appear on the screen. ABL should prevent this andextend the life of the picture tube.
<<Figure CA-11>>
Before sending processed RGB (red, green, & blue) outputs to the picture tube, ICX2200 integrates anyOSD (on-screen display), CC (closed caption), and PiP (picture in picture) into the video. At a particularpoint in the television�s scan across the picture tube, where the video is to display an OSD object, a fast-blanking (FB) pulse is sent from the microprocessor to the video processor at pin 14. This pulse of courseblanks the main screen video so that OSD can have precedence. Simultaneously, processed RGB from themicroprocessor enters the Jungle chip at pins 15, 16, & 17. This video fills in the blanked portion to be putonto the main screen.
Picture-in-Picture
A few notes concerning PiP are noteworthy here. First those sets that have PiP will not be able to producevideo without the PiP module installed unless the PiP section is jumpered out. J2201M, J2202M, W2203,and W2204 accomplish this. PiP signal enters the PiP module at pin 10 of connector PIPA1. This signal isconverted into RGB by the PiP processor and sent on to RGB OSD inputs of ICX2200. Pins 2 and 3 of
R2252M
C2235M
C2232M R2253MPROVL2202
C2236M R2254M
C2233MPROV
+9VSW
L1207
+9VF
C1220M C1222TP1203
+9VF
R1223M
C1223M C1224 R1224M
R1222M
CM
AFC
C2231
C2229M L2201 R2245MR2244M C2232
C2253 PROV
R2251
C2228M
1
2
3
4
5
DL2200
R2246M+9VSW
R2248M
W2206
C2230
R2250M
R2249M
Q2206
R2247M
C2227
W2207
Q2208
R2261M
R2262M
+9VF
R2260M
R2243M
C2224
Q2211PROV
+9VSW
R2270
W2200
C2225
R2242M
+9VFC2223
C2222 C2221
R2239M
R2236M
D2205 D2202
Q2209
R2265M
C2241R2263
R2264
+15VSW
R2237M
Q2204
+15VSW
R2241M
C2218
R2240M
R2234M
R2230MC2219
D2203
R2232M
Q2205R2238M
+15VSW
D2204
R2235
R2233
C2220
ABL
12 45
44
43
42
41
40
39
38
37
3621
13
14
15
16
17
18
19
20
CIN
AFT
YIN
DC
VSW-OUT
BLK/DET
VIN
ACL
TV-IN
ABL
VCXO
GND
FBLNK
ROSD
GOSD
BOSD
D-VCC
ROUT
GOUT
BOUT
ICX2200
VERTICALABL
EXT-VIDEO
COMPOSITEVIDEO-OUT
TVIN & CKT(Pin 47)
CHROMA-COMB
CA-14
CA CIRCUIT DESCRIPTIONSthe PIPB1 connector provide sync to the PiP processor. Pins 9 and 10 of the same connector allow I2Cbus communication between the PiP board and the microprocessor. PiP brightness however is controlledfrom pin 11 of the microprocessor. This controls the bias of Q2210, which varies a DC level on the OSDinput lines to ICX2200.
CR2201C2202MR2269M
C2242M
C2203
C2204
C2205
D2210
D2211
D2212
C2207
C2206M
R2210+9VSW
R2771PROV
C2239R2268M
Q2210
+9VSW
R2267M
PiP Brt
W2204
W2203
J2202M
J2201M
1 2 3 4 5 6 7 8 9 10
R2202M
C2240
R2201MR2205M
R2203M
R2207M
R2204M R2206M R2208M
PiP+SW
FASTBLANK
G+UP
B+UP
R+UP
1 2 3 4 5 6 7 8 9 10+9VSW +5VTuner
FLYBACK
VRAMP
SCL
SDAR2213M
R2218M
R2222M
R2256MD2207
R2257MD2208
R2258MD2209
R2255
Q2207
C2240MPROV
HALFTONE
Q2201
Q2202
Q2203
R2209MR2215MR2219M
1
2
3
4
5
R2221MR2217MR2211M
C2238M
12 45
44
43
42
41
40
39
38
37
3621
13
14
15
16
17
18
19
20
CIN
AFT
YIN
DC
VSW-OUT
BLK/DET
VIN
ACL
TV-IN
ABL
VCXO
GND
FBLNK
ROSD
GOSD
BOSD
D-VCC
ROUT
GOUT
BOUT
ICX2200
PIPA1
PIPB1
2C5
<<Figure CA-12>>
After PiP or OSD RGB enters the Jungle IC, it is combined with processed luma and chroma and then exitsICX2200 as main video for the picture tube. Red, Green, and Blue outputs are found on pins 19, 20, and21. Some CA receivers have a halftone circuit that taps off these lines. When Q2207 is switched on by asignal from the microprocessor, a limited amount of RGB signal is shunted to ground. The on-screen effectof this is a slightly dimmed video. This halftone signal is output in such a way to appear as a darkened buttransparent window surrounding the OSD.
Video Amplification
Before being fed into the CRT socket board via connector 2C5, RGB is pre-driven by Q2201, Q2202,and Q2203. The resulting signals are then sent to the main color driver transistors, Q5101, Q5102, andQ5103. These transistors have a high 300V collector to emitter breakdown voltage and a low collector tobase feedback capacitance (less than 3pF). Additionally, the series-parallel arrangement of both theiremitter and base circuits involving both capacitors and resistors allow for improved high and low frequencyresponse. The cutoff frequency of these drivers is 70 MHz. R5103, 5110, and 5119 from base to collectorhelp to increase bandwidth response of the drivers. These provide negative feedback from the output anddecrease gain. As gain decreases however, bandwidth response increases. The driver transistors are
CA-15
Video Processingpowered by the +215V source derived from the sweep transformer, but the actual DC voltage at thecollectors will be lower (+130 volts is a good ballpark figure) because of the resistors RX5104, 5111, and5122 and variations in the drive signal.
<<Figure CA-13>>
The emitter circuits of each driver are attached not to ground, but to a reference voltage of about +3V. Thisreference voltage is established by R5114 and D5101 and serves to set a black level for the cathodesaround +165 volts. The reference voltage must be relatively noiseless, so C5107 is used to eliminate anyinterference.
A number of the CA chassis provide an afterglow cutoff circuit on the CRT socket board. This circuitmakes use of the fact that with respect to the picture tube, G1 is the ground. Because C5107 takes arelatively long time to discharge, there is the possibility that the picture tube could continue producingelectronic emissions for a short time after the receiver is turned off. The afterglow cutoff makes use ofpower from the filament voltage (pin 4, connector 5F2). When the receiver turns off, the loss of this voltageturns off Q5104. This allows for a brief moment the G1 cathode to become more positive, leaving lesspotential on the other cathodes from any remaining voltage across C5107. C5110 determines the dead timeon response, and C5111 determines the rise time of the G1 voltage, both of which are between 10 and 30milliseconds.
1
12
11
109
8
7
65
4
CRT1
R5128PROV
W5101
1
2
3
4
5
Q5101R5101M
C5102M
R5102M
R5103
Q5102
R5108M
C5105M
R5109M
R5110
Q5103R5117M
C5108M
R5118M
R5119
RX5104L5101
C5101
RX5111
RX5122
R5115
R5107
R5123
+9 VSW
R5105M
R5106M
C5103M
R5112M
R5113M
C5106M
R5120M
R5121MC5109M
D5101 C5107
R5114
1
2
3
4
D5102PROV
+215V
R5127
C5111 L5102
C5110PROV
R5124MPROV
Q5104PROV
R5125PROV
R5126
L5103
R5116
C5104
DAG
+215V
Blue
Red
Green
G2
G1
BLUE
GREEN
RED
G2 Wireto Sweep
2
21
2
2
1
1
2
2
5F2
5C2
2
CA-16
CA CIRCUIT DESCRIPTIONS
Deflection Processing
The last portion of the video processor to be discussed is the deflection section. This is the part of the ICfrom which the vertical and horizontal deflection signals are derived. A critical power supply to this sectionis the +9VSW which feeds pin 26. Pin 24 emits the V-Ramp signal, from which both vertical sync for themicroprocessor and vertical drive for the vertical amplifier are developed. Refer to Q6002 in the micropro-cessor circuit for this process. Horizontal drive comes from pin 32. This ultimately drives the horizontaloutput transistor, which provides both horizontal deflection and power for the sweep transformer. Pin 31provides the sync pulse output to IC6000. This signal is really the horizontal sync pulse separated from therest of the video signal. It allows the microprocessor to determine whether or not the receiver has a validsignal. The flyback pulse is input to pin 30, thus allowing sweep feedback to the video processor�s deflec-tion section.
29
30
31
32
33
34
3522
23
24
25
26
27
28
VPULSE
NFB
VRAMP
VSEPFIL
HVCC
SCL
SDA
DGND
32FH
HAFC
H-OUT
H-SYNC
FLYBACK
SHUTDOWN
ICX2200
C2213M C2214M R2224MC2212MPROV
R2223
R2220
C2211MPROV
C2208
C2209 C2210M
R2216
+9VSW
R2212M
VRAMP
CLOCKDATA
R2225M
C2215M
D2201
R2226
C2554 PROV
CR2202R2231M
R2229M
C2217M
C2216
R2227M
FLYBACKSHUTDOWN
H-SYNCH-DRIVE
<<Figure CA-14>>
High-Voltage Protection
The last terminal of note here is pin 29, the x-ray protection/shutdown pin. If the potential at this pin risesabove +3.5 volts DC, the video processor will automatically clamp the horizontal output signal, shuttingdown the receiver. In the event that this occurs, the microprocessor will have to be reset before the televi-sion can be powered up again. Voltage at pin 29 is based on the voltage output from the flyback. Highvoltage shutdown will correspond with an over-voltage in the picture tube, which could otherwise begin toemit x-radiation.
CA-17
Deflection Control
Introduction
After deflection control signals are produced by ICX2200, they need to be modified and amplified beforethey are output to the deflection yoke. The CA chassis accomplishes this necessity for 25� to 36� televisionsets through the sweep transformer and the surrounding horizontal and vertical deflection circuitry.
Horizontal Drive
The Horizontal Drive (H-Drive) circuitry exists to control the drive signal to the Horizontal Output Transistor(HOT) as well as provide deflection to the horizontal yoke. Typically H-Drive operates at 15.734 kHz. Asit passes through the driver circuit, H-Drive signal is amplified to provide a sufficient signal to the HOTwithout causing it to go into saturation, thereby preventing distortion of the drive signal. H-Drive is pro-duced at pin 32 of the Video processor (ICX2200) and is passed to the drive circuit through R2227M, asurface mounted resistor. The signal enters the base of Q3201 which is directly coupled through its emitterto Q3202. Finally, the signal passes from the collector of Q3202 to the Horizontal Driver Transformer,TX3205, where voltage-to-current conversion and proper waveshaping occurs.
1
3 4
5
6
TX3205
C3206
QX3203
LX3202
CX3212
C3204Q3202
C3203
R3205
R3204 CX3205
RX3207
+18 VSW
R3203
C3202Q3201
C3201
R3202M
R3201M
H-Drive fromPin 32, ICX2200
Flyback Line toPin 30, ICX2200
H-Output toFlyback & Yoke
<<Figure CA-15>>
Flyback Transformer
From here, the signal switches the HOT (QX3203) on to provide a current shunt for the sweep transformer,TX3204 and the horizontal yoke. This switching alternately passes then blocks the B+ voltage providedthrough the primary winding of TX3204 to the collector of the HOT. The changing magnetic field in thesweep transformer caused by this action generates the high voltage (HV). This high voltage should normallybe between 26 and 30 kV. The particular value will correspond to the size of picture tube in the set. G2(screen control) and Focus voltages are tapped from a portion of the same winding that HV is derived from.As usual G2 and Focus may be adjusted by pots on the sweep transformer. These run to the CRT socketboard.
CA-18
CA CIRCUIT DESCRIPTIONSA number of secondary voltages are also provided by the sweep transformer�s action. Particularly, +215volts is supplied from pin 2 to the Video Output circuitry for driving color. In addition, +35V and +25V aresupplied, respectively from pins 6 and 9, for horizontal width and pincushion control circuitry (when neces-sary) and for vertical amplification circuitry. Filament voltage is also supplied from pin 7 into pin 1 ofconnector 2F5. Two other signals from the flyback are the ABL (pin 8) and the flyback pulse derived frompin 6. Refer to the video processor section for an explanation of these signals.
<<Figure CA-16>>
High Voltage Shutdown
Another winding from the flyback is used for high-voltage shutdown, commonly referred to as x-ray protec-tion. Activation of the HV shutdown circuit will occur when it detects a 4 to 6 kV increase in the high
From Flyback DX3006
CX3007
CX3003
RX3013PROV
RX3022
ZDX3004
RX3016
RX3015PROV
RX3008
DX3005
RX3009M CX3004
RX3010M
RX3211
DX3252CX3254
CX3253
+35V
To ShutdownPin 29, ICX2200
<<Figure CA-17>>
GND
G2
FOCUS
E
HV
TX3204
CX3207PROV
RX3209
B+ DX3201
C3209
RX3208
+215V
CX3208
+25V
D2104
C2112
C2111
RX2124
ABL
RX3217
RX3210APROV 1
2
3
4
+215 V
RX3211
CX3212
RX3212
DX3204
C3219
+35V
DX3252
CX3254 CX3253
CX3207A
RX3216
+33V
FlybackPulse
To HV Shut-Down Circuit
To VideoOutput
2F5
6
9
7
5
8
3
2
1
H-Output
CA-19
Deflection Controlvoltage. The HV shutdown circuit utilizes a rectified DC voltage across CX3003. This voltage is applied toa zener diode, ZDX3004, through a voltage divider consisting of RX3013, RX3015, RX3016, andRX3022. The actual value of the zener will vary according to screen size. When this DC voltage becomeshigh enough, the zener begins to conduct. The resulting voltage can be metered at pin 29 of ICX2200. Ifthe voltage in the shutdown pin is above +3.5 volts, the IC�s internal shutdown circuitry will trigger anddeactivate all horizontal signal from the IC, thereby shutting off the set. In this case, the microprocessor willhave to be reset before the television can be powered on.
Width and Geometry Correction
Width and east/west pincushion correction circuitry may be found on receivers with 27 - 36 inch picturetubes. Smaller sets have pincushion correction preset in the windings of their deflection yokes. Otherwise,width is controlled in the CA chassis digitally through the microprocessor, IC6000, using an internal pulsewidth modulator. The width control signal is emitted from pin 47 of the microprocessor and is supplied toC3250. This operation is very similar to the vertical size adjustment. The resulting DC voltage effects thebiasing of transistor Q3250, thereby changing the current in coil LX3201 and ultimately altering the width.
<<Figure CA-18>>
R3252
C3250
Q3250
R3255
Horz Size Pulse
RX3256
R3253
QX3251
R3257M
TP3200
R3259
CX3251
LX3201
DX3250DX3251
CX3252 CX3216
CX3256
C3217
H-Output from QX3203
LX3262
H Yoke
+35V
RX3215 CX3215
DX3203
RX3214 CX3218
C3255
R3258
W3203
W3200
W3201
W3202
Vertical RateDrive
VerticalParabola
The pincushion correction is accomplished using diode modulation. Key components of this circuit includethe width coil, LX3201; the horizontal yoke; CX3216 and CX3252; CX3217, used for S-correction;LX3262, for linearity; DX3250 and DX3251 as dampers; and QX3251 and CX3251, used for amplifyingthe vertical parabola waveform. This circuit uses the parabolic waveform from IC2100, the vertical ampli-fier, to shorten the horizontal scan lines on each end of the vertical trace. As the vertical trace is near itsextremes, voltage across CX3251 is increased. The result is a lower net voltage across the horizontal yokecoil which translates to less beam deflection. Conversely, when QX3251 modulates a lower voltage acrossCX3251, particularly when the vertical scan is closer to the middle of its trace, deflection is increased. The
CA-20
CA CIRCUIT DESCRIPTIONSresulting waveform for yoke current is a sawtooth with rounded peaks.
Vertical Amplification
Most of the vertical signal amplification is performed by the vertical amplifier, IC2100. This IC contains apower amplifier, a ramp generator, and a flyback generator and is supplied by +25 volts to pin 10. Theinitial vertical drive signal which should run at 60 Hz is developed from ICX2200, the video processor. Pin24 of ICX2200 is the vertical ramp (VRamp) source. This signal is inverted by Q6002 and sent as verticalsync to pin 2 of IC6000. It also travels as vertical drive to pin 3 of IC2100 through R2101. The verticaloutput signal to the yoke comes from pin 1.
<<Figure CA-19>>
RampGenerator
VoltageRegulator
PowerAmp
BufferStage
ThermalProtection
FlybackGenerator
R31
2
3
4
5
6
7
8 9
10 11
ClockPulse
IC2100
R2101
R2104
C2130MC2101
R2103
C2102
R2106M
R2107M
R2105
C2103
R2108
R2109M
R2110M
R2111M
CX2105
DX2101 CX2110
RX2117
C2106
R2118 R2119
R2114
R2112M
R2113
RX2115 RX2116
C2104 C2108
C2107
+25 V
Vertical RateDrive for PinCorrection
To CRTProtectionCircuitry
VerticalOutput
VerticalABL
VerticalSize
VerticalDrive
Vertical size is also amplified within IC2100. IC6000 controls vertical size using a pulse width modulatedsignal emitted from pin 48. The signal generates a DC voltage across C2101. This DC controls verticalheight using circuitry inside IC2100. As the width of the pulse changes, a corresponding change occurs inthe DC level. In this manner, vertical size may be controlled in the on-screen servicers menu.
CA-21
Deflection ControlCRT Protection
CRT protection is provided for the CA in circuitry off the vertical amplifier. In case of a damaged IC2100or a shorted CX2107 for example, this circuit will prevent damage to the CRT by shutting the microproces-sor off. In turn, this action shuts down the television receiver. The circuit is composed of C2109, DX2102,DX2103, R2120M, R2121, R2122M & R2123. Pin 11, the pump-up, of IC2100 emits a pulsing wave-form. DX2102 rectifies this waveform to a DC voltage across C2109. After passing through the voltagedivider network formed by R2121 and R2122M, the voltage can be found on pin 13 of IC6000 and shouldmeter between +3.6 and +5.1 volts. Should the voltage be outside this range, CRT protection will trigger.If the CRT protection circuitry is triggered at power on, the television will turn off in 3 seconds. If thisoccurs, it will be necessary to reset the microprocessor before the television will turn on. Resetting themicroprocessor may be accomplished by removing AC to the set for a couple minutes.
R2120M R2121 R2123
R2122MC2109
DX2102
DX2103
+5 VSB
To CRT ProtectionPin 13, IC6000
Pin 11,Vertical Amplifier,IC2100
<<Figure CA-20>>
Part Location Part # NotesTX3204 095-04372-01 Refer to Service Manual
095-04601-01 for Corresponding ModelsQX3203 121-01383 All ModelsIC2100 221-00992-01 All Models
<<Table CA-3>>
CA-22
CA CIRCUIT DESCRIPTIONSAudio Amplification
There are three audio circuit configurations used in the various CA chassis: mono, stereo, or MTS (Multi-channel Television Stereo). While few CA receivers are monophonic sets, the mono audio circuit bearsmentioning due to the fact that it is used in each of the three circuit variations.
IC804, the audio amplifier IC and heart of the mono audio circuit, is capable of both mono and stereo audioamplification. IC804 has dual audio inputs (pins 2 and 5) and, naturally, dual outputs (pins 10 and 7).These outputs drive 8-ohm, 5-Watt speakers. The audio amplifier utilizes +18 volts audio (+18 AUD) as itspower supply on pin 9. Its characteristic voltage gain is 50 dB. However, to eliminate potential noiseproblems, R854M and R864M are used in conjunction with feedback capacitors C852 and C862 to limitvoltage gain. Such an arrangement allows use of a higher power audio signal that is less prone to noiseinterference. Maximum output to the speakers should not be more than 3 Watts. Pin 3 of IC804 connectsthe Mute line from pin 14 of the microprocessor to the audio circuit. A high signal on the base of Q800 willturn that transistor on, lowering voltage on pin 3 and causing the amp IC to mute the audio.
1
2
5
6 4 8 7
103 9IC804
R861MC861
R862M C865MR852MC855MC852
R854M
R864M C862
C843
+18VAUD
W140
C842 C841
Q800
Mute
1
2
3
4C854
C864
C853
C863
R853
R863
R843
R851M *C851*
Left Audio*(MTS orStereo Only)
To TVSpeakers
9S4CompositeAudio or RightAudio
<<Figure CA-21>>
When IC804 is used as a mono amplifier, composite audio comes through C861 into pin 2. When used in astereo or MTS receiver, pin 2 serves as the right audio channel input, and pin 5 as the left. C861 and C851(for non-mono sets) are used to pass audio but block any DC. Surface mounted capacitors, C855M andC865M, are used to set the gain cut frequency to approximately 13 kHz. Voltage dividers consisting ofR861M and R862M for the right channel and R851M and R852M for the left channel limit the maximumsignal input to 42 mVrms. Maximum output from the stereo processor is normally 490 mVrms, whichwould be too high an input for IC804.
CA-23
Audio DevelopmentIn the mono circuit, composite audio is fed directly from pin 2 of ICX2200 into the audio amplifier circuit.However, on stereo and MTS models, composite audio is fed into IC1400A or IC1400 respectively. Herethe composite sound can be separated into left and right audio channels.
Stereo Processing
In stereo receivers, IC1400A receives composite audio through C1436 into pin 11. Because the 490mVrms composite audio signal from ICX2200 is too high for the audio processor input, the voltage dividerconsisting of R1421M and R1422M limit the signal to 245mVrms. This audio processor is controlled bythe microprocessor via serial clock and data lines connected at pins 3 and 4. IC1400A is powered by the+9VSW at pin 16. Its right and left channel output exit the IC at pins 1 and 2.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
LSOUT-R
LSOUT-L
SDA
SCL
DGND
MAININ
MAINOUT
PCINT1
PCINT2
PLINT
COMPIN
VGA
IREF
GND
SAPTCVCC
SUBOUT
STIN
NDISETC
SAPOUT
SAPIN
VE
VEWGT
VETC
VEOUT
VCAIN
VCATC
VCAWGT
NC
NC
IC1400A
C1415R1405M
C1414
C1417
C1419
C1422R1407M
C1424R1408M
C1428
C1426
C1427
+9VSW
C1433M C1430
R1425M
C1421
C1420R1406MC1416
C1425
R1404M
C1413
R1422M
C1436 R1421M
C1418
C1435M
PROV
C1434MPROV
R1401
R1402
To AudioAmp IC
Clock &Data Lines
CompositeAudio In FromICX2200, Pin 2
<<Figure CA-22>>
External audio input on the stereo chassis is passed to the audio amplifier via IC1401, a microprocessor-controlled switching IC. This IC is powered by the +9VSW at pin 9. When the external inputs are presenton a receiver, processed audio from IC1400A will come into the switching IC at pins 5 and 12. External(or auxiliary) audio enters the switching IC at pins 7 and 10. If an auxiliary source is detected by IC6000, asignal from pin 44 of the micro will trigger pins 2 and 4 of IC1401 to switch from internal to external audioinputs. Whichever audio source is selected will be passed from pins 8 and 11 to the volume controlIC1402.
CA-24
CA CIRCUIT DESCRIPTIONS
<<Figure CA-23>>
IC1402 is powered by the +18AUD at pin 4. Pins 5 and 8 receive the audio input, while the output forright and left channels come from pins 1 and 3 respectively. This volume IC is controlled by a DC levelfrom pin 46 of the microprocessor. Pin 46 emits a pulse width modulated signal that is rectified andsmoothed by D1401, R1420M, and C1438. The resulting DC voltage is applied to pin 7 of IC1402. Thisvoltage will vary from +0.5 to +5 volts DC. The gain of this IC is 12dB.
IC Location Part # NotesIC804 221-00598-01 All ModelsIC1400 221-01127 MTS ModelsIC1400A 221-01382 Stereo ModelsIC1401 221-01171 Stereo ModelsIC1402 221-01380 Stereo Models
<<Table CA-4>>
12
11
10
9
8
7
6
5
4
3
2
1
CH-2
CH-1
IC1401
+9VSW
1
2
3
4 5
6
7
8
IC1402
C1423
C1437
+18AUD
R1417
ZD1405 C1439
C1455
J1406M *
C1456
C1429
J1407M *
C1438
R1420M
R1419M
R1418M
+5VSBF
D1401
R1418
R1413
R1412
C1409
C1410
L RAudio Outputto IC804
* For Stereo Chassisexcluding 9-2064, 2065
Provisional on 9-2064, 2065
Audio SwitchPin 44, IC6000
External Audiofrom Jack Pack
Left & RightStereo Audio(Pins 1,2, IC1400A)
Volume ControlPin 46, IC6000
CA-25
Audio Development
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
2425
36
26
27
28
29
30
31
32
33
34
35
37
38
39
40
41
42
43
44
45
46
47
48 BASSL2
TRE-R
TRE-L
SURRIN
SURROUT
LSOUT-R
LSOUT-L
NC
SDA
SCL
DGND
SAD
MAININ
MAINOUT
NC
PCINT1
PCINT2
PLINT
COMPIN
VGR
IREF
GND
SAPTC
VCC
BASSL1
BASSR2
BASSR1
SURRTC
TVOUT-L
TVOUT-R
AUX2-L
AUX2-R
AUX1-L
AUX1-R
VLTC
VLDC
VCAWGT
VCATC
VCAIN
VEOUT
VETC
VEWGT
VE
SAPIN
SAPOUT
NOISETC
STIN
SUBOUT
IC1400
C1401M
C1402M
C1404M
C1416
C1435MPROV
C1434MPROV
R1401 R1402
R1425M
C1421
C1420R1406M
C1418
C1436
C1413
R1404M
C1425
R1421M
R1422M
+9VSW
C1433MC1430
C1403M
C1406M
C1431M
C1409
C1410
R1412R1413
R1409M
C1432
C1415
C1414
R1405M
C1417
C1427
C1426
C1428
C1419
C1422
C1424
R1407M
R1408M
ExternalAudio In
CompositeAudio In FromICX2200, Pin 2
Clock &Data Lines
To Audio &External Amps
MTS Processing
For MTS chassis, IC1400 serves as the sound processor. It features mono, stereo, or SAP settings. Italso features adjustable bass and treble levels, balance adjustment, sound-right audio limiting, front surroundsound, and speaker cut-off. Furthermore, whereas internal and external source switching is accomplishedby a separate switching IC for the stereo sets, the MTS is capable of internally switching between varioussources.
<<Figure CA-24>>
IC1400 is powered by the +9VSW at pin 24. Composite audio enters through C1436 at pin 19. Thissignal is reduced by a voltage divider consisting of R1421M and R1422M. I2C bus control (serial clockand data) from the microprocessor enters the MTS processor at pins 9 and 10. Information on these linescontrols those adjustments as described above as well as the volume. Right and left channel auxiliary inputfeeds into pins 39 and 40. Audio outputs come from pins 6 and 7 and feed the amplifier circuit in themanner described above.
CA-26
CA CIRCUIT DESCRIPTIONSExternal Audio Output
The output pins here also feed the variable audio output circuitry. This common emitter amplifier has a gainof 12 dB. Q1402 and Q1403 are used to amplify left and right channels respectively. Power for thisamplification stage is provided by Q1401, which uses the +15VSW. To reduce popping on the monitors,the switching of Q1401 is briefly delayed by an RC network formed by R1440M and C1440.
<<Figure CA-25>>
Q1401
+15VSW
R1440M
R1441M
C1440
Q1402R1442M
R1443M
R1444M
R1445M
R1446
C1441M
C1443
C1442
J1402MPROV VM-OUT-L
Q1403R1447M
R1448M
R1449M
R1450M
R1451
C1444M
C1446
C1445
J1450MPROV
VM-OUT-R
L(7)
R(6)
Stereo Signalsfrom IC1400,Pins 6 & 7
CA-27
Flowcharts
Start1. No Power
Plug receiverinto AC source.
ReplaceFX3401.
ReplaceFX3402.
ReplaceTX3401.
Replace ICX3400,QX3401, DX3406,DX3407, DX3408.
ReplaceICX3402.
Yes
No
No
No
No
No No
No
Yes
Yes
YesYes Yes
Yes
Yes
ReplaceIC6000.
Check Q3404,Q3402.
ReplaceICX3401.
ReplaceICX2200.
Refer to shutdowntroubleshooting.
No
No
No
No
Yes
Yes
Yes
Yes
Is ACconnected?
Does FX3401conduct?
Is B+ presentat CX3420?
Does FX3402conduct?
Is QX3401shorted?
Is pin 3,ICX3400
switching?
Is +18VSBpresent across
CX3424?
Is +5VSBpresent across
C3426?
Does pin 32,IC6000 emit aDC pulse at
startup?
Is +18VSWpresent across
CX3430?
Is +9VSWpresent across
C3429?
Is Horz & Vertdrive presenton pins 32, 24of ICX2200?
CA-28
CA TROUBLESHOOTING2. Shutdown
Start
Does the setpower up formore than 2seconds?
Does the DClevel at pin 29,ICX2200 rise
above 3.5 volts?
Checkmicroprocessor
ciruitry.
No
Yes
Check HV-shutdown circuit,
sweeptransformer.
Does the setshutdown afterjust 3 seconds?
Check IC2100 &CRT protection
circuit.
Yes
Yes
No
No
Is B+ running ata constant DC
level?
ReplaceICX3400
No
Yes
CA-29
Flowcharts3. No Tuning Start
Are all tunervoltages
present? (Referto schematics.)
Check tunerpower supplies.
Is IF present atpin 11, TU6000?
Does changingthe tuner fix the
problem?
Check clock anddata lines.
Replace IC6000if clock & data
lines OK.
Is IF present atpins 7, 8,ICX2200?
Check IF line.Replace Q1200,
U1200 ifnecessary.
Is IF present atpin 47,
ICX2200?
Does Q1201 testOK?
ReplaceICX2200.
Replace Q1201
Refer to No Audio and NoVideo Troubleshooting.
Yes
No
No
No No
No
No
Yes
Yes
Yes
Yes
CA-30
CA TROUBLESHOOTING4. No Video Start
Is raster presenton the screen?
Is 1.07 kVp-psignal present oncollector of HOT?
Is regulated B+present across
CX3420?
Check powersupply.
Check TX3204.Check HOT andH-drive circuit.
Is there video atpin 37, ICX2200?
Check Q1201,Q1202
Is compositevideo present onpin 41, ICX2200?
ReplaceICX2200.
Is 0.76 Vp-p lumasignal present atpin 43, ICX2200?
Check Q2206and/or DL2200.
Are RGB signalspresent on pins3-5, connector
5C2?
Are Q2201, 2202,2203 OK?
Replace Q2201,2202, 2203.
Is +215 VDCpresent across
C5101?Check TX3204.
Check G2adjustment.
Yes
No
Yes Yes
Yes
Yes
Yes Yes
Yes
Yes
No No
No
No
No
No
No
No
CA-31
Flowcharts
Check audiopower supply.
Is +18AUDvoltage presenton pin 9, IC804?
Start
Does Q800 testOK?
Does DC levelchange at pin 14,
IC6000, whenspeaker cut-off is
toggled?
Is compositeaudio present atpin 2, ICX2200?
Is compositeaudio present atComp-In pin of
IC1400(A)?
Is audio presenton LSOut-R/L
pins ofIC1400(A)?
Is audio enteringIC804 at pins 2,
5?
Replace Q800.
Replace IC6000.
Checkcomposite audio
line.
Does Q1201 testOK?
Is +9VSIFpresent on pin48, ICX2200?
Replace Q1201.
Check powersupply.
ReplaceICX2200.
Replace IC804.
ReplaceIC1400(A).
Check L/R audiolines.
5. No Audio
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
Section 2:CB Chassis
CB Chassis Safety Guidelines
X-RADIATION
To prevent possible exposure to radiation caused by excessive CRTAnode voltage, the CB Chassis incorporates a �High Voltage Shut-down� circuit. This circuit senses the level of flyback pulse from�Flyback Transformer� representative of the actual high voltage onthe CRT anode. When this level exceeds a predetermined voltage,the circuit shuts down the horizontal drive, preventing further gen-eration of anode voltage. In this condition, the horizontal drive is�latched� off. The drive will remain off until the microprocessor isreset.
SHUTDOWN CIRCUIT OPERATION
This shutdown circuit operates by means of sample HV taken frompin 6 of the sweep transformer TX3204. This sample of voltage isrectified, filtered and compared with a reference voltage(fixed byZDX3004 by the transistor QX3002. When the HV reaches the maxi-mum permitted voltage, the transistor QX3002 enters in conductionmode like consequence the transistor QX3001 also enters in conduc-tion. When QX3001 enters in conduction, the flyback pulses at theentrance of the video processor are 1 volt or less,the the TV goes outand enters in shutdown mode.
When the shutdown circuit is operating, the microcontroller willprevent the TV from being turned on again unless the microcontrollerhas been restarted by disconnecting the TV from the AC line.
CRT ANODE HIGH VOLTAGE MEASUREMENT PROCEDURE
Each CRT screen size has its own safe operating Anode Voltage andshutdown voltage. Critical Safety components (designated with an�X� in the component designator) are designed to operate the CRT ata safe operating Anode voltage and provide proper shutdown thresh-olds . If replacement of any of these components are deemed neces-sary, it is important to use original type Zenith replacement compo-nents. After replacement is made, confirm proper Anode voltageusing the following procedure.NOTE: The CB chassis does not have a bleeder resistor to discharge
the Anode voltage. High voltage can remain on the CRTAnode long after power is turned off. Before removing theCRT anode connection, turn off and unplug the television,then discharge the CRT Anode to DAG ground.
Measurement of the CRT Anode voltage must be performed using ahigh impedance high voltage meter, with no visible raster on thescreen, and operating at nominal horizontal scanning frequency.Connect a strong broadcast signal (or TV signal generator operatingat 15.734kHz horizontal scanning rate) to the RF input.
After discharging the CRT, connect a high impedance high voltagemeter to the CRT anode. Turn the television �on� and confirm a goodsignal is being displayed . Reduce Brightness and Contrast settingsuntil the picture is well extinguished.
Observe the Anode voltage meter reading and compare with thetable below for the proper CRT screen size. If the voltage reading ishigher that the maximum, verify circuit component values and properoperation.
7'6))2 &��:(' ,:�231 ,:�1%<7->) ���&)%1� /: /:
�� ������������ �� ���� ������������ �� ��
�� ������������ �� ������ ������������ �� ����
'31432)28�0):)0�6)4%-6
13(90)�0):)0�6)4%-6�320=
SAFETY CIRCUIT TEST PROCEDURE
This shutdown circuit operates by means of a sample of HV takenfrom pin 6 of the sweep transformer TX3204. This sample of voltageis rectified, filtered and compared with a reference voltage ( fixed byZDX3004) by the transistor QX3002. When the HV reaches the maxi-mum permitted voltage, the transistor QX3002 enters in conductionmode; like consequence the transistor QX3001 also enters in con-duction.
When QX3001 enters in conduction, the flyback pulses at the en-trance of the video processor (pin 18) are attenuated. If thisatenuattion is so that the flyback pulses at the entrance of the videoprocessor are 1 volt or less, then the TV goes out and enters inshutdown mode.
When the shutdown circuit is operating, the microcontroller willavoid that the TV is turned on again unless the microcontroller hasbeen restarted by disconnecting the TV from the AC line.
Equipment required:
a) Video Generator.
b) HV DC meter (0 to 40 KV, high Z).
c) External variable power supply (0V to 200 VDC @ 5Amps mini-mum).
d) 1 Giga ohm, 5%, 2W film resistor.Note: The external power supply may require a diode for blocking
voltage from the chassis power supply to the external powersupply. The diode should be connected between the positiveoutput of the external power and B+ of the chassis. Thecathode should be facing the B+ of the chassis. Therecommended diode is Part No. 103-00339-04A (400 V ofVRRM @ 3 Amps of average rectified forward current).
SHUTDOWN SAFETY CIRCUIT
CB-i
RX32111
470 pfdCX3002
DX3002
5.6KRX3005
1.5KRX3003
PROVRX3006
PROVRX3004
QX3002
RX3002M33K
CX320347uf
RX3007M8.2K
ZDX3400
DX3001RX3001M
10K
CX3001M0.01
QX3001
+9VSW
0.1 / 25vC2241M
PROVR2223M
VID
EO P
RO
CES
SOR
D2205R2224M
8.2KR2222M
4.7K
PROVC2215M
PROVC2214M
IC2200
FROM SWEEP TRANSFORMER
FROM FLYBACKPULSE
HP / XRAYPOT
CB-1
Power Supply
Introduction
The CB chassis is a cold chassis designed to support 27�, 32�, and 36� receivers. Its power supplyfeatures a controlled turn-on MOSFET gate driver circuit, direct B+ regulation, thermal protection circuitry,over-current protection (OCP), over-voltage protection (OVP), over-load protection, provision for futureuniversal power input (85VAC � 265VAC), and software controlled degaussing.
As with many SMPS circuits, this one activates as soon as it is connected to AC line current via plugconnector 3R8. Depending on the screen size, the CB can draw anywhere from 125 to 140 watts from theline supply. AC operating tolerances range between 90 Vrms and 135 Vrms. Note that while most of thefunctional portion of the CB chassis is considered to have a cold ground, the rectifier and primary side of theswitch-mode power supply have a hot ground.
Switch-Mode Power Supply Primary Side
FX3401, a 4 amp/250 volt fast-blow fuse, protects the CB chassis from AC line surges. EX3401, thespark gap, also provides some protection for the set. Incoming AC passes the fuse and is filtered byLX3401, CX3401, and CX3402. The switch-mode power supply (SMPS) uses a fairly standard bridgerectifier arrangement to develop raw B+, the voltage that runs the SMPS and ultimately the entire televisionset. DX3400 is the packaged bridge used in 32� and 36� sets. The 27� sets use discrete diodes DX3401,3402, 3403, and 3404. Rectifier output (raw B+) will be somewhere between 127.3 and 190.9VDC.This VDC is smoothed by and can be measured across CX3407.
DX3402
DX3403
DX3401
DX3404RX3401
CX3406
C3403
CX3407
CX3404
CX3405
CX3402
B+ VDC
LX3401
CX3401EX3401
RX3400
CX3400
FX3401
3R8
To SM Regulator
DX3400
To DegaussingCircuit
<<Figure CB-1>>
ICX3412 is the switch-mode regulator IC used to develop the numerous individual power supplies off thesecondary side of TX3401, the chopper transformer. The same chopper is used in all three of the CB sizes.This transformer isolates the hot portion of the chassis from the cold portion. Raw B+ feeds into pin 18 ofthe chopper. The other end of this coil, pin 11, connects with pin 3 of ICX3412. Pin 3 is the drain of theinternal MOSFET that drives the chopper transformer, while pin 2 serves as the MOSFET source.
ICX3412 functions when the voltage on pin 4 reaches +16 volts DC. This voltage is developed onCX3410. As it starts, the regulator pulls nearly 20mA of current from CX3410, causing its voltage to
CB-2
CB CIRCUIT DESCRIPTIONSbriefly drop. However, as the regulator begins to operate, it drives the chopper, and power derived frompin 13 of the transformer is drawn through DX3407 to maintain the voltage on CX3410. Overload andover-voltage protection are both internal to the regulator IC, and sensed through pin 4. Should either ofthese conditions occur, and latch will deactivate the oscillator inside ICX3412, thus eliminating any powersupplied by the chopper.
ICX3412
TX3401B+VDC
RX3416
To Rectifier Ckt
LX3410
LX3417PROV
LX3402CX3412CX3409 CX3418
PROV
CX3408
CX3411
DX3406
DX3407
DX3408PROV
C3413PROV
RX3405
RX3403 RX3404
RX3415PROV
RX3406
RX3407
CX3410
1
23
4
ICX3403
SecondarySide, SMPS
To SecondaryFeedback Ckt.
16
13
11
18
12345
<<Figure CB-2>>
Pin 1 of the regulator IC allows feedback input for voltage regulation. Control voltage is supplied to this pinvia ICX3403, an opto-isolator that receives output information from the secondary side of the chopper,particularly from the regulated B+. This feedback is accomplished by the programmable reference device,ICX3406. The output from this IC is fed to the opto-isolator, which then communicates this signal back tothe switch mode regulator circuit. The output voltage error derived from ICX3403 puts a DC bias acrossRX3405 and a drain current ramp on RX3403. The net effect of both the output voltage error and drain
OCP/FB Comp
INH Comp
4
1
3
5 2
OCP/FB
GND
Vin
Source
Drain
DRV
221-00060-03ICX3412
DRV Bias
OVP
TSDBias
UVLO Latch
Oscillator
<<Figure CB-3>>
CB-3
Power Supplycurrent ramp is input into pin 1 of ICX3412. This signal is then used to determine how regulation shalloccur as described below. OCP is also sensed using this pin. To prevent a false over-current detection atstartup however, a constant current sink has been included in the regulator. This measure is necessary dueto a current spike that often occurs at startup due to primary capacitance discharge.
The switch-mode regulator makes use of the resonant frequency set up by the chopper transformer andCX3408. This resonant frequency as well as the internal oscillator determines the nature of the MOSFET�sswitching. Hence, the term quasi-resonant may be applied to this regulator. Regardless of the terminologyused, the IC regulates voltage based on the following simple rule: duty cycle on-time reduces as voltagerises, while duty cycle off-time reduces as load rises. In this manner, correct voltage is maintained at thechopper transformer. The regulator�s fundamental switching frequency is 20 kHz, but when the receiver isswitched on, the regulator will operate as high as 100 kHz.
Switch-Mode Power Supply Secondary Side
The secondary side of TX3401 makes use of four separate windings, each with its own half-wave rectifier,to develop the various voltages required by the television set. As a result there are four primary stand-byvoltages (VSB): B+ (typically +130 volts), +12VSB, +15VSB, and +22VSB. The +15 and +22VSB areeach protected by 3A/250V, slow-blow fuses, FX3402 and 3403. The B+ line has sufficient protectionfrom the switch mode regulator. RX3423 is a fusible resistor that protects the +12VSB line.
<<Figure CB-4>>
R
A
C
ICX3406
RX3423
TX3401
1
23
4
ICX3403
CX3432PROV
LX3403
C3419
D3410 B+
CX3420
CX3431
+15VSB
RX3409
RX3427
CX3414PROV
CX3417PROV
CX3416
CX3415
RX3428
LX3415 D3409
ICX3404PROV
RX3408
RX3421
B+
CX3427
+12VSB
L3406
C3425
OUTIN1
2
3
ICX3402
C3426
+5VGEM
L3412
+5VPiP
W3403
L3407
+5VSBM+5VTUNE
FX3402
FX3403
LX3405DX3418
C3423+22VSB
C3422C3435
D3419
PDD
LX3404 D3411
C3421
CX3424
L3414RX3417
CX3428 CX3430
+15VSB
OUTIN1
2
3
ICX3401
D3416C3429
Q3405
W3405
L3409
W3404
+9VIF
+9VSB
R3425M R3426
+9VSW
LX3416PROV
+9VSWF
CX3436
D3417
Q3402R3418M
Q3404
R3412M
+15VSB
L3408
+15VSW
C3433
OUTIN1
2
3
ICX3405
C3434
+12VSW
RX3413
R3410
R3411
L3410
L3411
B+ +33VSB
-14VDC
+14VDC
-14AUD
+14AUD1
2
3
4
B+
+15VSW
IQB32B44WIQB36B44WONLY
4W9
±14 Volts DCfrom Flyback
Power ControlPin 32, IC6000
9-21049-21059-2106ONLY
3
6
8
5
7
9
1
4
3
2
1AudGND
To PrimaryFeedback Ckt.
PrimarySide, SMPS
CB-4
CB CIRCUIT DESCRIPTIONSThe B+ provides power for deflection via the horizontal output transistor (HOT), QX3204, and for thetertiary voltages that come from the flyback transformer, TX3204. It also develops the +33VSB for thetuner through RX3413. The +12VSB is regulated down to +5VSB by ICX3402. This +5 volt sourcepowers the microprocessor and EEPROM (IC6000 and IC6001 respectively), the Gemstar® board, thePiP board, and the tuner. The +15VSB is used as is to power sweep correction, horizontal drive amplifica-tion, and the ABL circuitry. It is also regulated by ICX3401 for +9V and by ICX3405 for +12VSW. Bothof these voltages are used as various video and IF supplies. The +22VSB is used to power the audioamplifier.
Two other voltages should be named here, although they are developed from the sweep transformer,TX3204. Namely the + and � 14VDC pass through the secondary of the switch mode power supplysection. These become the +/- 14AUD volts that power the variable audio output amplifier when they passthe series resistor and inductor arrangement shown on the schematic.
Some of the above voltages are switched on when the television powers up, rather than when it is justplugged in. These include +9VSW, +9VIF (some models), +9VSWF, +15VSW, and +12VSW. Theseare switched upon receiving a power on DC level from pin 32 of the microprocessor, IC6000. Thisswitches Q3402, which in turn activates both Q3405 and Q3404.
Degaussing Control
Degaussing is software-controlled by a signal from IC6000. When the receiver is switched on, pin 33 emitsa 760 ms signal that closes the degaussing relay, KX3401, via Q3403. This allows a brief moment of ACcurrent to magnetize the degaussing coil before the thermistor, THX3415, limits the coil�s power.
<<Figure CB-5>>
KX3401
DX3405
Q3403
THX3415
+15VSB
R34192
1
FilteredAC Line
DegaussingControl, Pin 33,IC6000
3T8 -- ToDegaussingCoil
Part Location Part # NotesICX3401 F-52403 All ModelsICX3402 F-53046 All ModelsICX3403 162-00028-01 All ModelsICX3405 221-00167-05A All ModelsICX3406 221-00265-03A All ModelsICX3412 F-53857 All ModelsTX3401 095-04576 All Models
<<Table CB-1>>
CB-5
Microprocessor Control
Introduction
The CB chassis employs IC6000 as its microcontroller. All end user and servicer controls are accessedusing this IC. While most of its functions will be described in terms of how they are used by other devices inthe receiver, a number of facts concerning the microprocessor and its input devices will now be presented.
The microprocessor�s job is to communicate control instructions and feedback information to and fromvarious other processors and input devices in the set. These include the video, audio, PiP, Gemstar®, audio& video switch ICs, the tuners, the EEPROM, the keyboard and IR detector, and the reset IC. Some ofthese use a direct connection via either switch, variable pulse, or DC level for communication. Others relyon the I2C bus, also known as serial clock and data bus. IC6000 provides 2 sets of clock and data lines.The first set is pins 37 and 39, and the second is on pins 36 and 38.
Input Devices
The IR detector demodulates pulses from the 40 kHz modulated carrier and sends the pulses to pin 15 ofthe microprocessor. There a special algorithm interprets the pulses as the various commands they represent.The keyboard is only slightly more complicated in its operation external to IC6000. It works by varyingvoltage on only two input pins (7 and 8) using resistor networks. A/D converters inside the micro interpretthe different voltages. Because voltage detection is used rather than active keyboard scanning, keyboardradiation is not a problem, but maintaining a +5VSB to within ±4% is critical. Both keyboard and IRinformation enter the CB chassis through connector 2K6.
Microcontroller
VDD is provided to pin 27 of the microprocessor from the +5VSBF supply. While this voltage is relativelylow, IC6000 is fairly demanding in terms of current. This same voltage powers the keyboard and IRdetector. The +5VSBF is also used as analog VDD and enters the micro at pin 18.
IC6002 serves as a reset IC for the main microprocessor. Note that it comes in a transistor type package.It accurately resets the micro after a power failure is detected. Pin 30 is the reset signal input for IC6000.The micro enters reset state after detecting a low on pin 30 of 2µS or more.
When the micro receives a power on signal from either the keyboard or the remote, the degaussing controlpin 33 turns on the degaussing circuit for 760ms. At the same time a constant voltage level from pin 32turns on the switched voltages in the power supply.
Horizontal and vertical synchronization pulses are fed into pins 1 and 2. These provide the microprocessorthe current sweep location of the beam, which is necessary to correctly interrupt main video for varioustypes of on-screen display (OSD). Neither of these sync pulses come directly from the IC2200 where theyare first produced. Horizontal sync is actually fed back from the sweep transformer on the flyback pulseline. Vertical ramp signal coming from pin 5 of IC2200 feeds the base of Q6002. Sync is produced on thecollector and fed to the vertical amplifier and through R6006M to the V-Sync pin of the micro. OSD orCC (closed captions) are sent as processed RGB (red, green, & blue) from pins 50, 51, and 52. At thosetimes it is necessary to blank out part of the main video, a fast-blank (FB) pulse is sent to the video proces-
CB-6
CB CIRCUIT DESCRIPTIONSsor from pin 49 along with the processed RGB. An exception to this occurs when Gemstar® is displayed.Under that circumstance, the fast-blanking pulse without RGB is sent to the video processor via theGemstar® board.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
36
26 27
28
29
30
31
32
33
34
35
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52HSYNC
VSYNC
AFC
N/C
SD2
SD
KEY1
KEY2
AFC2
Y/C1-SENSE
Y/C2-SENSE
Y/CF-SENSE
CRT-PROT
MUTE
IR DET
N/C
N/C
AVDD
HLF
RVCO
VHOLD
CVIN
CNVSS
XIN
XOUT
VSS
R
G
B
FB
PiP-BRIGHT
N/C
N/C
N/C
AUD-SWAP
N/C
GM-RESET
YUV/SWITCH
H/T
SCL1
SCL2
SDA1
SDA2
IDENT
N/C
DEG-CTL
POWER
N/C
RESET
OSC-OUT
OSC-IN
VDD
IC6000
C6012MC6013
L6001
+5VSBM +5VSBF
CRY6001
R6034M
C6010M C6011M
C6008MR6080
R6033MC6009
R6032M
C6007M
R6031MC6006
C6005M
R6030L6007
+5VSBF
C6037
C6044
1 2 3 4 5
L6004
R6015M
R6016M
R6027
C6003M
L6005
C6035PROV
C6036M
R6010
C6040MC6002M
C6059M
Q6001
C6001MR6003M
R6004
R6001M
R6002M
Q6002 Q6004
R6007M R6005M R6006M
C6026M
R6008M
+5VSBF
D6002
C6058M
R6009M
R6017M
R6014M
R6011M
+5VSB
C6004M
C6022M
C6034M
R6063
R6064
Composite Video
C6060M
R6051
+5VSBF
R6052M
C6061M
R6013
C6041M
C6042M
C6043M
R6069M
R6070M
D6003
R6012M
V-Sync
V-RampFlyback
SD2SDAFC-Main
AFC2
CRT-ProtectMuteY/C1-SenseY/C2-SenseY/C-Front-Sense
2K6EXTERNAL KEYBOARD
<<Figure CB-6>>
The CB chassis features a halftone function that dims video surrounding OSD. This halftone circuit isdescribed in the video section, but is controlled by a DC level from pin 40.
Closed captioning display is accomplished in the microprocessor by use of the composite video into pin 22.Here a data slicer extracts the caption information and outputs it to the RGB pins when captioning is re-quested by the user. Note that when OSD needs to be on the screen, such as after a channel change orduring a volume change, the OSD will have priority, and CC will mute until OSD turns off.
Pins 5 and 6 are signal detection pins. When the either of the chassis� two tuners detects a bona-fide signalto the video processor, it separates horizontal sync signal from the IF and sends it to this portion of themicroprocessor. It can then be used to determine if a certain channel is carrying a valid active broadcast.
Automatic frequency correction (AFC) is sent to the microprocessor via pin 3 and pin 9 (for the secondtuner IF). The DC level on either pin tells the microprocessor if it needs to communicate an adjustment to
CB-7
Microprocessor Controlthe corresponding tuner to allow for clearer channel reception. The ideal voltage level here should bebetween +2.25 and +2.5 volts.
<<Figure CB-7>>
IC6000 provides CRT-protection for the set through pin 13. Operation of this shutdown depends on a DClevel from the CRT protection circuit off the vertical amplifier circuit. Should the vertical IC2100 fail, theDC level will no longer be present. In this situation, the CRT-protection latch will shut the receiver downthree seconds after detecting the failure. This circuit will prevent the CRT from burning a horizontal phos-phor line in the center of the screen or, worse yet, cutting the yoke end of the tube off completely.
The remainder of the I/O pins on IC6000 are briefly described here. Where necessary, a more detaileddescription will be provided in the circuit descriptions to which they relate. Pins 10, 11, and 12 are used asS-Video (Y/C) detection for the two Y/C jacks on the back and the Y/C jack on the front (where avail-able). Pin 48 emits a varying DC level that changes the bias on Q2211, effecting the PiP brightness of theRGB input to IC2200. Audio swap is accomplished by pin 44, which varies a DC level to a transistor arrayin the IF section. This array allows the audio signal being heard by the user to be switched between theprimary and secondary IF. Pin 42 controls the Gemstar® module�s reset function. Pin 41, the YUV-SWvaries a DC level on pin 36 of IC2200 to make it switch main video between separated luma and chroma
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
36
26 27
28
29
30
31
32
33
34
35
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52HSYNC
VSYNC
AFC
N/C
SD2
SD
KEY1
KEY2
AFC2
Y/C1-SENSE
Y/C2-SENSE
Y/CF-SENSE
CRT-PROT
MUTE
IR DET
N/C
N/C
AVDD
HLF
RVCO
VHOLD
CVIN
CNVSS
XIN
XOUT
VSS
R
G
B
FB
PiP-BRIGHT
N/C
N/C
N/C
AUD-SWAP
N/C
GM-RESET
YUV/SWITCH
H/T
SCL1
SCL2
SDA1
SDA2
IDENT
N/C
DEG-CTL
POWER
N/C
RESET
OSC-OUT
OSC-IN
VDD
IC6000
C6012MC6013
L6001
+5VSBM +5VSBF
C6017
R6037M
C6016 C6056M D6001
C6014MR6059M
CRY6002PROV
L6002
R6060MR6035MC6015M
C6018M C6045M C6046M
Deg-CtlPower-Ctl
C6024M
C6025M
C6033M
C6023M
R6081M
C6065MR6024MC6067M R6088M C6091M
Q6003 J6001MC6046M R6023M
C6063M
C6055M
1
2
3
R6062MPROV
R6061MPROV
D6004
PROV
R6071MPROVC6054M
C6038M
C6039M
R6040M
R6058M C6057M
R6068
C6068M C6052M C6062M C6053M
VCC
GND
OUT
IC6002
Power-Fail
YUV-SwitchGM-Reset
PiP-BrightnessAud-Swap
Halftone
FB-MicroB-MicroG-MicroR-Micro
FB-PiP
4Q9
IQB32B44WIQB36B44W
ONLY
CB-8
CB CIRCUIT DESCRIPTIONSsignals entering IC2200 at pins 4 and 2 respectively and component video entering at pins 37 through 39.Note here that component video cannot be used as PiP. Lastly, pin 14 of IC6000 switches a DC level toalter the mute state of the audio amplifier.
Memory
The EEPROM, IC6001, is a small but vital part of the CB receiver. This 512 byte memory chip is respon-sible for storing servicer adjustments, channel information, and user settings, even when power is removedfrom the set. This information is transferred on the clock and data lines from the micro into pins 5 and 6.The EEPROM is powered by the +5VSBF source at pin 8.
1
2
3
4 5
6
7
8
IC6001
R6049
R6050M
+5VSBF
L6003
C6020 C6021M
1
2
3
4
5
+5VSBF
R6072R6039M
C6019M
R6046M
R6045M
R6047M
R6048M
C6047MC6048MC6049MC6050M
IDENTDATA2DATA1CLOCK2CLOCK1
R6041R6042MR6043R6044M
CLOCK2DATA2
(IC6000)3536373839
Clock & Datafor IF, Videoand Audio
4G9
<<Figure CB-8>>
IC Location Part # NotesIC6000 221-01388 All ModelsIC6001 221-00745-05 All ModelsIC6002 221-01177A All Models
<<Table CB-2>>
CB-9
IF Receiver
Introduction
The CB chassis utilizes two tuners in order to provide PiP without requiring a second external source. Thisis with the provision that the receiver�s antenna input is receiving multi-channel input. For example, a cabledecoder box usually only provides a single channel input. Although the television possesses two tuners,each is receiving an identical single channel, so a second external source would have to be used here if theuser desires his PiP to be different from the main screen. On the other hand, a standard cable input or evena regular antenna provides multiple channels that each tuner can demodulate individually.
The IF (intermediate frequency) section can be broken up into a half for each tuner. Those part designa-tions numbered from 1200 through 1249 relate to the primary tuner, WT1200. Part designations from1250 to 1289 apply to the secondary tuner, WT1250.
Tuner
For the most part, each tuner is fairly identical to the other as it relates to the rest of the chassis. Eachcorresponds respectively to IF IC1200 and IC1250 (IFPs or IF processors), which are also identical. IF
1
2
3
4
5
6
7
8
9
10
11
12 13
14
15
16
17
18
19
20
21
22
23
24DET-OUT SIF-IN2
1ST-SIF-AGCFM-DET
IF-AGC2 SIF-OUT
RF-AGC-ADJ VIDEO-OUT2
IF-IN1 EQ-FILTER
GND
EQ-INIF-IN2
APC-FILTER
SIF-IN1 VIDEO-OUT1
VCC VCO2
RF-AGC-OUT VCO1
AFT1 AFT-OUT
AFT2 IF-AGC1
IC1200
R1218MC1208
TP1206
C1210MR1208M
R1207M
+9VSW
C1209
R1206
C1211M L1202VCO
R1211M
C1212M
R1212MC1213TP1207
L1203
U1201 R1209M
R1210M
C1214M
R1216M
Q1200
C1215M
U1202
R1219MPROV
R1226M R1225M
W1200PROV
+9VSW
R1214
R1213M
R1222M
R1217M
CR1200
L1204
C1214C1222M
R1288M
C1219M
C1220M
R1223M
R1224M
1
2
3
4 5
6
7
8
U1200
C1201M
C1205M+9VSW
C1203M
C1204
C1221MPROV
R1202
C1200M
R1203M
R1201M
L1200
C1290
C1202M
C1207ML1201AFC
C1206M
R1204
R1205M
+5VTune
+33VSW
TP1200
ZD1230C1230
C1231M
C1232 C1233M
J1201MC1234
PROV
C1235M
PROV
TP1201
C1236C1238M
PROV
C1237M
PROV
R1230M
R1231M
SDASCL
Q1290
Q1293
Q1291
Q1292
R1297M
Audio-Swap
R1298M
+9VSW
R1299PROV
C1294
PROV
R1291M
R1293M
R1292M
R1290M
Comp-Aud
R1294M
C1292Comp-Aud2
R1296M
C1293M
R1289M
R1295M
Q1241
Q1240
+5VSB
AFC-Main
C1240
R1240M
C1241M
R1242M
R1241M
C1242
R1246M
C1244M R1245M
C1243M
R1244M
R1243M
Luma-SD
SD-Main
+9VSB +9VFil
L2901
C2935 C2936M
TP1205
TP1202
AGCDelay
AntennaInput
To 2ndTuner
To MainTuner
Splitter
IF-VideoMain
Main Tuner
11
10
9
8
7
6
5
4
3
2
1
WT1200SCL Main-Tuner
<<Figure CB-9>>
CB-10
CB CIRCUIT DESCRIPTIONScomes from pin 11 of the tuner, is filtered, and is fed into pins 5 and 6 of the IFP. AGC (automatic gaincontrol) voltage is applied to tuner�s pin 1 from pin 10 of the IFP. The +33VSB tuning voltage is applied topin 9, while the +5VTune processing voltage is on pin 7. Clock and data lines from IC6000 communicatewith the tuner on pins 4 and 5. In some receivers, the secondary tuners use the +9VIF at pin 6.
IF Processing
Each IFP is powered by the +9VSW on pin 9. After IF is received at pins 5 and 6, sound IF is separatedfrom picture IF emitted from pin 17. It reenters the IFP through pin 24 and finally exits through pin 1 as acomposite audio signal. Composite audio from each IFP enters a switching transistor array with partdesignations 1290 through 1299. The audio-swap line from the microprocessor controls Q1292. Thistransistor switches the rest of the array between composite audio from either the primary or secondarytuner.
<<Figure CB-10>>
Two variable coils are available with each IF processor for adjusting AFC or VCO. Use caution whenadjusting these, and be certain to mark their initial position in case they need to be adjusted back to theirprevious setting. A potentiometer is also available off pin 4 of the IFP. This adjusts the AGC delay insidethe processor.
1
2
3
4
5
6
7
8
9
10
11
12 13
14
15
16
17
18
19
20
21
22
23
24DET-OUT SIF-IN2
1ST-SIF-AGCFM-DET
IF-AGC2 SIF-OUT
RF-AGC-ADJ VIDEO-OUT2
IF-IN1 EQ-FILTER
GND
EQ-INIF-IN2
APC-FILTER
SIF-IN1 VIDEO-OUT1
VCC VCO2
RF-AGC-OUT VCO1
AFT1 AFT-OUT
AFT2 IF-AGC1
IC1250
R1265MC1270
TP1255
C1271MR1266M
R1267M
+9VIF
C1285
R1268
C1272M L1254
VCO
R1272M
C1273M
R1271MC1274TP1254
L1255
U1252 R1270M
R1269M
C1277M
R1273M
Q1251
C1276M
U1253
R1286MPROV
+9VIF
R1278M
R1276M
R1256M
R1257M
CR1250
L1251
C1259
C1261M
C1260M
R1259M
R1258M
C1264M
C1265M+9VIF
C1267M
C1266
R1261
C1262M
R1260M
R1262M
L1252
C1263M
C1269ML1253
AFC
C1268M
R1263M
R1264M
+5VTune
+33VSB
TP1250
ZD1250C1256
C1255M
C1257 C1254M
J1250MC1258 C1253M
TP1251
C1250
C1288M
PROV
C1287M
PROV
R1251M
R1250M
SDA2SCL2
Q1252
Q1253
+5VSBF
IF2-Video
AFC2
C1278
R1279M
C1279M
R1281M
R1280M
C1280
R1284M
C1282M R1285M
C1281M
R1283M
R1282M
1
2
4
5
3
U1251
L1250
PROV
+9VIF
Comp-Aud-2
SD2
TP1253
TP1252
2nd-IF-Tuner
11
10
9
8
7
6
5
4
3
2
1
WT1250
AGCDelay
CB-11
IF ReceiverThe remaining outputs of the IF processor are the AFC control to IC6000 from pin 14 and the IF videosignal which passes through the AV-switch (IC2900) as it travels to the comb filter. AFC output voltagecauses the microprocessor to determine any frequency corrections the tuner needs to make for a bettersignal. A portion of the luma from the IF-video is separated and filtered for the purposes of signal detectionat pins 5 and 6 of IC6000. From the main video signal, this separation occurs after the comb filter stage,where composite video exits IC2900 at pin 34. Signal detect information (SD) is then separated from theluma by transistors Q1240 and 1241 and their surrounding circuitry. For the second video signal, luma istaken immediately from the IF video signal out of IC1250 and separated by the circuitry including Q1252and 1253.
Part Location Part # NotesIC1200 221-00792 All ModelsWT1200 175-02770 All ModelsIC1250 221-00792-01 All ModelsWT1250 175-02770 All Models
<<Table CB-3>>
CB-12
CB CIRCUIT DESCRIPTIONS
Jack-Pack
The CB chassis provides multiple means for connecting external sources that supply video and audio signal.These provisions include two composite video (CV) inputs, two S-Video (Y/C) inputs, component video(YUV) input, corresponding left and right channel audio inputs for each video input, and, in some models, afront input jack featuring CV, Y/C, and stereo audio inputs. Additionally, a two-channel variable audiooutput is provided. This portion is discussed further in the audio circuit description.
Audio/Video Switch IC
In order to handle the multitude of incoming signals from the jack-pack, as well as the two internal IFsignals, the CB chassis employs an analog audio/video IC2900. This IC is powered at pin 18 by the+9VSW. While switching is analog, IC2900 is digitally controlled through the I2C (serial clock and data)bus connection at pins 26 and 27. This data stream communicates both user selections for signal input aswell as microprocessor priority commands. These priority directives may be explained by the followingexample.
<<Figure CB-11>>
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
36
26
27 28
29
30
31
32
33
34
35
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54LINE2
VINE2
RINE2
LINE1
VINE1
RINE1
LINE4
VINE4
RINE4
VINE3
LINE3
RINE3
VINS1
LINS1
YINS1
RINS1
CINS1
GND1 ROUT1
YOUT1
LOUT1
VOUT1
YIN1
CLAMP1
VINS2
LINS2
YINS2
RINS2
CINS2
VCC CLAMP2
YIN2
ROUTD
LOUTD
CIN1
COUT1
VINS3
LINS3
YINS3
CINS3
RINS3
GND2
MUTE CIN2
O3
COUT2
ROUT2
YOUT2
LOUT2
VOUT2
SDA
SCL
I/O2
I/O1
IC2900C2934M
C2930M
C2929M C2931M
C2928MR2944M
C2933
C2932R2960M
R2958M
C2927
C2926
C2925
R2945M
R2940
C2924M
C2938M
R2943M R2933M C2923M
Q2902
R2934M
R2935M R2936M
+9VSW
Q2904
R2956MJumper R2957M
R2955M
R2937M
R2954M
Q2901
R2938M R2939M
+9VSW +9VSWF
Q2903
R2952M R2953M
IF2-Video
CV-Micro
IF-Video-MainY+C/CV-PiP
Luma-MainLuma-SD
Left-SWRight-SWY-Comb
CV-Comb
C-Comb
Chroma-Main
1 2 3 4 5 6 7 8 9R2931M
R2932M
ZD2903
R2930 Y/C-Front-SenseC2922M
C2921M
C2913 R2924
C2919MPROV
C2914R2925
R2973MC2917MPROV
C2920M R2928
C2916R2926
R2974MZD2908
R2927
Jumper
C2918MPROV
C2915R2923
ZD2903
C2901R2902 Jumper
ZD2904
R2901
C2902 R2904
R2969M
C2905M
C2903 R2906
R2970M
Y/C1-Sense
SDASCL
R2907
ZD2901
Y/C2-Sense
C2907R2909Jumper
C2908M
R2911
R2910
R2908
ZD2906
+9VSW
C2912
C2937R2914 Jumper
ZD2905
R2916
C2906 C2910R2921 Jumper
R2918C2909
C2911MR2922
R2919
R2912
R2971M
R2972M
ZD2910
R2920M
See Component VideoJackPack Section
11
23
18
6
5
4
10
2
19
9
8
3
7
17
12
7
24
12
24
17
Y/C1-In
Aux1-R-In
Aux1-L-In
Video1-In
Y/C2-In
Aux2-R-In
Aux2-L-In
Video2-In
4A8
IQB27B42WIQB27B44WIQB36B44W
ONLY
CB-13
A/V Switching
Suppose the user has composite video connected to the Video 1 input and S-Video connected to the S-Video 1 input. If the user selects video source 1 in the customer menu, the receiver must choose betweenthe CV and the Y/C signal. Each Y/C input has a sensor line that feeds the micro. If the micro detects thepresence of Y/C on video 1, IC6000 will direct the A/V switch to use that Y/C signal instead of the CV.Thus if it is present, Y/C has priority over CV.
IC2900 features three functional input arrays for jack-pack signal. Each array consists of left and right (L/R) channel audio input, CV input, and Y/C input. Additionally, the A/V switching IC provides another inputfor the dual IF-video signals and input for the Y (luma) portion of the component video input as well as itsassociated audio. CV, Y, and IF inputs should scope near 1.0Vp-p. Color burst from the Y/C inputs aswell as audio inputs should scope about 300 mVp-p.
For outputs, IC2900 uses pins 39 and 41 for L/R channel external audio. This is fed to IC1400, the audioprocessor and is used if the user selects a jackpack source. Pin 41 serves as the PiP video output. PiPvideo is sent as a composite video signal. However, if the PiP source is S-Video, IC2900 internally com-bines the Y and C signals into a CV signal. PiP CV should have a strength of 2.0 Vp-p at pin 41. Mainvideo is output to the video processor on pins 32 and 34 as chroma (C) and luma (Y), respectively. Theluma signal should be 2.0 Vp-p while chroma is about 600 mVp-p.
Composite or IF video input to the IC cannot be passed to IC2200 as composite video. Rather, the A/Vswitch passes CV or IF video via pin 41 through the comb filter section, where it is separated into luma andchroma and returned to pins 38 and 30 of IC2900. Voltage at pin 41 should be 2.0 Vp-p. The separatedsignal is then sent to IC2200 as Y and C along the main video lines. It should be mentioned that pin 34 alsosends the luma signal to IC6000 so that closed captioning (CC) and synchrony information can be extractedfrom it.
Part Location Part # NotesDL2400 223-00045 IQB27B42WIC2400 221-01040 IQB27B44WIC2900 221-01053 All Models
<<Table CB-4>>
CB-14
CB CIRCUIT DESCRIPTIONSComponent Video
Component video is handled differently than the other jackpack inputs. The CB lacks conversion circuitryto make component (YUV) signal into CV. For this reason, component video cannot be used for PiP,which requires CV input, and is furthermore not separated (or combined) into luma and chroma throughIC2900. YUV is directly input to IC2200 at pins 37 through 39. This arrangement necessitates the use ofa YUV switch from the microprocessor to the video IC. With respect to the A/V switch, however, the Ycomponent is still input to pin 2 and, when in use, is output as composite video to the microprocessor. Asmentioned before, this information is used to obtain CC and video synchrony. Moreover, the U componentmust be amplified to an acceptable level to be used by IC2200. Q2906 and 2907 serve this purpose usingthe +9VSWF for power.
C2904
C2940 R2905
C2939 R2903
R2976MR2975M
123
R2946
R2948R2950
Jumper
R2949
R2951
R2947
ZD2907
1 2 3 4
1 2 3 4
C2941 Q2906
R2961M
R2964M
R2964M
R2963MC2942
R2965M
+9VSWF
Q2907 C2943
R2966M
R2967M
R2968M
CR-InYUV-InCB-In
Pins 1-3IC2900A/V Switch
4C2
2C4
151413
24
17 212016
YUV-In Cr-In Cb-In R-In L-In
<<Figure CB-12>>
Comb Filtering
CB receivers use either a 1H glass comb filter, DL2400, or a 2H digital comb filter, IC2400. Both separatecomposite video into luma and chroma more efficiently than simple chroma traps and band-pass filters. Thisallows for video that is relatively free of color and luma distortion in high detail video objects. Comb filtersare better equipped to distinguish color from high-frequency luma, and can thereby reduce the crosstalkbetween the two.
For sets using DL2400, CV from IC2900 enters pin 2. Chroma is output to pin 3 while luma exits the filterat pin 5. Receivers that possess DL2400 still utilize a color trap (R2470M, L2411, and C2471M) and aband-pass filter (R2463, L2410, and C2442M) to ensure purity of both chroma and luma before it isreturned to the A/V switch.
CB-15
A/V SwitchingOn sets using the digital comb filter, CV is fed into an A/D converter at pin 5 of IC2400. This IC is pow-ered by the +5VTune at pins 3, 12, 20, and 27. Output for chroma is at pin 23 and for luma is at pin 25.Both are further cleaned by transistor circuitry that is powered by the +12VSW. Finally, �combed� lumaand chroma are returned to the A/V switch.
<<Figure CB-13>>
1
2
3
4
5
6
7
9
8
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15KILLER
VSS2
VDD2
CKIN
FILT
CBPF
VENH0
VENH1
1LINE
CORING
1/2VDD VDD3
VSS3TEST1
CLAMPC BIAS3
COUTBIAS1
A/DIN BIAS2
YOUTVREFH
VDD1 VREF1
VDD4VSS1
VREFL VSS4
IC2400C2409M
C2412M
C2414M
C2415MR2405M
C2417M
C2418MR2408M
C2413
R2409M C2419M
R2407M C2446M
R2406M
+5VTune
L2413
C2445
C2444MC2443
L2412
+5VTune
L2415
R2448M R2449M
C2449M
C2448
R2404M
Q2401
+12VSW
R2403M
R2402M
C2407M
L2402
C2405M
R2401M
C2406M
R2400M
C2451MPROV
FSCCV-Comb
C2423M
C2424M
R2446MC2447M C2455
+5VTune
R2454M
C2459
R2461M
R2460M
+12VSW1
2
3
4
5
DL2400
C2461M
C2450
R2471M
R2470M
L2411
C2471M
Q2413
Q2414
Q2411
+12VSW
2 3
46
L2409
23 4
6
L2408
Q2404
R2447M
R2436M
R2445M
R2444M
R2457M
R2439M
R2440M
C2439M
R2441M
R2463
C2442ML2410
C-Comb
Y-Comb
+12VSW
R2455M
R2426M
R2427M
Q2405
R2416M
R2417M
R2458M
C2452
R2472M
Q2406
+12VSW
R2473M
R2474M
R2430M
C2453
**See Note!
IQB27B42WIQB32B42WIQB32B84RIQB32B86RIQB36B42WIQB36B86R
**Note!Boxed AreasONLY for these:
CB-16
CB CIRCUIT DESCRIPTIONSIntroduction
The CB chassis video features include two-tuner PiP, comb-filtered video, auto kine bias, half-tone video,and direct component video input to the video processor. Certain receiver models also include 2H digitalcomb filtering, Gemstar�s® Guide Plus, front A/V inputs, and scan velocity modulation.
At the heart of the video circuitry is the NTSC video processor, IC2200. This video IC is powered by the+9VSWF at pins 33 and 44. Its primary means of communication with the microprocessor is via the serialclock and data (I2C) bus at pins 34 and 35.
Video Development
The NTSC video IC handles multiple types of video input and processes the output as RGB (red, green,and blue). Specifically, IC2200 receives luma and chroma (Y/C) information on pins 4 and 2 respectively.This input generally serves as main screen video. However, the video processor�s main video input can beswitched via pin 36 to use component video (YUV) that is input to pins 37 through 39. Secondary video(PiP) is input to the video processor as RGB through pins 26, 27, and 28. The PiP daughter board receivesvertical and horizontal sync information and thereby sends fast-blanking (FB) pulses to pin 25 of IC2200when main video needs to be blanked for PiP. In this sense, PiP has priority over main video. The micro-processor and, where used, the Gemstar® board also send OSD input as RGB to the video processor intopins 29 through 31 with FB signals from either source entering the video IC at pin 28.
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
TP5VBK
R6090PROV R6090M
+5VGEM +5VSBM
C6090
R6091M
Q6090
Q6091
R6092M
R6093M
R6094M
PDD
+5VPiP +9VSWF
+5VGEM
W6001
W6002W6003 W6004
C2290PROV
L2205PROV
R2297MPROV R2296M R2295M R2294M
R2290
R2291M
R2292M
R2293M
SCLSDA
VRamp
Y+C/CV-PiP
R-PiPG-PiPB-PiP
FB-PiP
FB-MicroB-MicroG-MicroR-Micro
B-OSD+GEMG-OSD+GEMR-OSD+GEMFB-OSD+GEM
Power-FailFlybackV-SyncIF2-VideoResetSCL2SDA2IRBLST2IRBLST1
Jumpers Used inNon-GemStar
Module ReceiversOnly
IQB27B44WIQB32B44WIQB36B44W
ONLY
GemStar Connectors& PDD Circuitry
PiPB1
PiPA1
GEM2
GEM1
<<Figure CB-14>>
Before video can be completely processed, it must also receive ABL (automatic brightness limiter) and ACL(automatic contrast limiter) information. IC2200 receives this at pin 3. Unlike many receivers, the CB usesa single input to control both ABL and ACL. For simplicity, pin 3 may be referred to as the ABL pin. ABLis first taken from pin 8 of the flyback transformer, TX3204. The signal is made positive across C2206 bythe voltage divider formed by R2201, R2212, and R2213. If current level in the picture tube penetrates the
CB-17
Video Processinglimiter threshold (1.5 mA for 27�, otherwise 1.6 mA), the corresponding voltage across C2204 triggers thelimiter circuitry internal to IC2200, thus reducing output level (and therefore the contrast and brightness) ofthe RGB signal. ABL helps to prevent blooming in the sweep that would otherwise occur as high currentdraw lowers the sweep voltage. It also serves to extend the life of the picture tube.
<<Figure CB-15>>
Another factor involved in determining the RGB outputs is the AKB (automatic kine bias) circuit whichfeeds into IC2200�s pin 21. This signal is derived from the CRT circuitry. It uses feedback informationdeveloped by three scan lines of video, one per color, in the over-scanned area above the video image. TheDC level returned is compared with an internal reference voltage that is determined in the service menusettings for optimum black levels. RGB color is adjusted accordingly and finally output on pins 22 through24 of the video IC.
IC Location Part # NotesIC2200 221-01394 All Models
<<Table CB-5>>
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24 25
36
26
27
28
29
30
31
32
33
34
35
37
38
39
40
41
42
43
44
45
46
47
48APED
C1IN
ABLIN
CVBS1/YIN
VTIM
MONOUT
NC
XTAL
FSCOUT
APCFIL
VCC2
TV/C2IN
COMB-CIN
YCLAMP
COMB-YIN
GND1
EW
REF EYIN
ER-YIN
EB-YIN
GND2
CVBS2/Y2IN
ABLFIL
VDP
VDN
VMOUT
REG
SCP
HP/XRAYPROT
YUV-SW
SDA
SCL
VCC1
R2IN
G2IN
HD-OUT
AFCFIL
IKIN
ROUT
GOUT
BOUT YS1
B1IN
G1IN
R1IN
YS2/YM
B2IN
IC2200
R2252M
C2231M
C2232M
C2230
C2234
C2233M
C2235M
C2236M C2237
L2202C2239
C2238M
R2253M
CRY2201
C2240M
R2256
R2254MR2255M
Q2208
+9VSWF
R2282
PROV
R2281PROV
C2240C2241
L2201
+9VSWF
R2251
R2250
C2228MPROV
C2229MPROV
C2225M
C2224M
C2223M
R2271M
R2242
D2211 D2212 D2213
C2222M
C2220M
C2219M
R2261M PROV
R2262M
PROVR2263M
PROV
R2266MPROV
R2265MPROV
R2264MPROV
C2245R2280M
+9VSWF
R2287
PROVQ2211
R2279M
R2278M
C2208M
C2209M
C2210M
R2206M
C2201
C2248M
C2247M
L2204
R2286M
PROV
R2285
R2283 C2249M
L2203
R2284M
C2250
C2204
+15VSW
B+
R2204M
R2213R2202C2206
R2216PROV R2212
R2201
Q2210PROV
R2205PROV
R2267MPROV
R2269MPROV
R2268M PROV
C2244
PROV
R2203M
C2216M
C2217
ABL
Luma-MainChroma-Main
FSC
CB-InCR-In
YUV-InYUV-Switch
SDASCL
R-OSD+GEMG-OSD+GEMB-OSD+GEM
PiP-Brightness
FB-OSD+GEM
FB-PiPB-PiPG-PiP
R-PiP
Pins 21-24Refer to RGBOutput Ckt
IQB32B44WIQB36B44WIQB27B44W
ONLY
IQB27B42W IQB32B86RIQB32B42W IQB36B42WIQB32B84R IQB36B86R
ONLY
HandInsertedComponent
CB-18
CB CIRCUIT DESCRIPTIONS
Before this processed video is pre-driven by transistors Q2205, 2206, and 2207, the video signal can bedimmed by the half-tone circuit. This circuit draws a limited amount of current when Q2209 is switched onby the half-tone pin 40 of IC6000. The half-tone circuit generates a rectangular area surrounding OSD inwhich video is present but shaded.
1 2 3 4 5 6 7
+12VSW
+9VSW
R2233
R2236
D2214
C2251Q2205
Q2206
Q2207
R2237M
R2234M
R2240M
R2257M
R2258M
R2259M
D2206 D2207 D2208
R2260
Q2209
C2243MPROV
Halftone
VID B+
Q2201PROV
D2204PROV
R2241M
PROV
ZD2201
R2231M
Q2202
J2201MPROV
R2245M
R2247M
R2244M
R2245M
R2243M
1: +12VSW2: Setup3: AKB-Sense4: GND5: R-Out6: G-Out7: B-Out
2C5 Key
IKINPin 21
B-OutPin 24
G-OutPin 23
R-OutPin 22
2C5
<<Figure CB-16>>
Video Amplification
After the RGB signal is pre-driven, it is sent to the CRT socket via connector 2C5. This socket boarddelivers the filament, focus and G2, and RGB video signals to the picture tube. Besides the AKB circuit, theCRT socket has an afterglow suppression circuit.
Each color is amplified in its own circuit section on the CRT board. The red amplifier section consists ofthose parts designated with 5120 through 5130. Green uses part designations 5140 through 5150 and blueuses 5160 through 5170. The video signal is cascode-amplified by a dual transistor arrangement for eachcolor. +235 volts from pin 1 of the 5F2 connector supplies power to the cascode amplifiers.
For example, Q5141 and 5142 amplify green signal. Frequency response is the major concern with regardto Q5142. By itself, Q5142 would tend to lose gain at higher frequencies. To remedy this problem,C5141M is added to the series-parallel network on Q5142�s emitter. This capacitor along with R5144Mprovide an improved response to higher frequency signals, while the resistor, R5143M, improves lowerfrequency response in the cascode amplifier. The resistor network formed here by R5145M and R5143Maffect the black level of the green. Q5141 also helps bandwidth of the cascode amplifier. It reducesfeedback caused by parasitic capacitance in Q5142. Q5141 has a very low feedback capacitance, lessthan 3pF, and a nearly 300V collector to emitter breakdown voltage. Its cut-off frequency is about 70MHz. Its collector passes green signal on to the push-pull coupling amplifier formed by Q5143 and Q5144and finally to the cathode through CRT1, the actual socket on the picture tube. This example applies to allthree color signals, with their respective components substituted.
CB-19
Video Processing
AKB signal is derived from the collectors of Q5124, 5144, and 5164. These are fed back to the AKBcircuit via pin 5 of the 5C2 connector and processed in the manner described above.
The CRT board also features a setup jumper for optimal G2 adjustment. The purpose for it is to force DCvoltage on the cathodes to be equal to the CRT cut-off voltage (170-190 volts DC with respect to G1).When jumped, the G2 setup circuitry grounds any incoming video signal. The servicer can then adjust theG2 pot, located on the flyback transformer, TX3204, until retrace lines just start to appear on the screen.Going back to the example of the green circuit, current then flows in Q5141, D5142, L5141, and RX5146.It is at this point that raster is almost cut off. When the jumper is released, the AKB circuit adjusts the colorwith the highest CRT cut-off voltage to the G2 setup voltage. The other two colors will be just slightly lowerdepending on their cut-off settings in the service menu.
1
12
11
109
8
7
65
4
CRT1
1
2
3
4
1 2 3 4 5 6 7
+235V
Q5121
Q5123
Q5101
Q5124
1
2
D5122
D5121
RX5129PROV
RX5128
R5173Jumper
L5121
RX5126
RX5127
L5122
RX5130
Q5122
R5122M
R5121M
Q5141
Q5143
Q5144
D5142
D5141
RX5149PROV
RX5148
R5172Jumper
L5141
RX5146
RX5147
L5142
RX5150
Q5142
R5142
C5143PROV
R5141M
Q5161
Q5163
Q5164
D5162
D5161
RX5169PROV
RX5168
R5171Jumper
L5161
RX5166
RX5167
L5162
RX5170
Q5162
R5162M
C5163PROV
R5161M
C5123PROV
+12VSW
R5165
R5164M
R5163M
C5161M
R5145M
R5144M
R5143M
C5141M
+12VSW
+12VSW
R5125M
R5124M
R5123M
C5121M +12VSW
C5105
R5107
C5104PROV
R5110PROV
+235V
C5100
W5101R5101PROV
R5106
C5103
G2W5102PROV
DAG1DAG2
C5106
D5101R5109
R5104
R5103
R5102
R5105
+235V
C5102PROV
C5101
L5101
C5164PROV
5C2 KEY
1: Blue2: Green3: Red4: GND5: AKB_Sense6: Setup7: 12VSWDGND
SETUP
BLUE
GREEN
RED
5F2
5C2
<<Figure CB-17>>
The afterglow suppression circuit is used to prevent any residue light that might otherwise remain on thescreen after shutdown. This circuit takes advantage of the fact that the filter capacitor on the +235V linetakes a relatively long period of time to discharge. The loss of filament voltage at shutdown triggers theswitching of Q5101, which then briefly interrupts the G1�s (pin 5) path to ground. The residue voltage on
CB-20
CB CIRCUIT DESCRIPTIONSC5101 causes the G1 to become more positive. Since G1 is otherwise considered ground for the CRT, thisaction reduces any remaining CRT potential, thus eliminating afterglow. C5101 controls the rise time of thiscircuit, while C5106 controls the dead-time on response.
Deflection Processing
IC2200 also supplies deflection signals to drive the sweep section. Vertical drive is supplied in the form ofpositive and negative ramp signals on pins 13 and 14 respectively. Simultaneously, a vertical ramp is alsosupplied from pin 5 of the video processor. This vertical signal is converted into vertical sync, directly bythe PiP board, and through transistors Q6002 and 6004, which then provide the v-sync to the microproces-sor and the Gemstar® board.
<<Figure CB-18>>
Horizontal drive comes from pin 19 of IC2200. This signal drives the horizontal output transistor (HOT).The flyback line taps off of the HOT collector to provide feedback to pin 18 of the video processor.Furthermore, this same flyback signal provides horizontal sync for the PiP, Gemstar®, and, through Q6001,the microprocessor. Pin 18 of IC2200 also serves the second purpose of protecting the set from highvoltage. While pin 18 normally receives horizontal feedback signal, a high voltage situation will activateQX3001. The collector of this transistor will then attenuate that signal. If attenuation lowers the signal to1.0 Vp-p or below, IC2200 will shutdown the CB receiver. Lastly, in terms of horizontal deflection, pin 11
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24 25
36
26
27
28
29
30
31
32
33
34
35
37
38
39
40
41
42
43
44
45
46
47
48APED
C1IN
ABLIN
CVBS1/YIN
VTIM
MONOUT
NC
XTAL
FSCOUT
APCFIL
VCC2
TV/C2IN
COMB-CIN
YCLAMP
COMB-YIN
GND1
EW
REF EYIN
ER-YIN
EB-YIN
GND2
CVBS2/Y2IN
ABLFIL
VDP
VDN
VMOUT
REG
SCP
HP/XRAYPROT
YUV-SW
SDA
SCL
VCC1
R2IN
G2IN
HD-OUT
AFCFIL
IKIN
ROUT
GOUT
BOUT YS1
B1IN
G1IN
R1IN
YS2/YM
B2IN
IC2200
C2240C2241
L2201
+9VSWF
R2214M
R2215M
C2213
Q2203
+9VSWF
C2212M
R2219M
R2220M
R2218
1
2
C2252MPROV
R2225M
+9VSWFR2226M
H-Drive
VDNVDPE/W
V-Ramp
Pin 18: Refer toHV Shutdown Ckt
PROVISIONAL ONIQB32B44WIQB36B44W
ONLY
4X9
CB-21
Video Processing
D2205
R2224M
R2222M
R2223MPROV
C2241M
C2214MPROV
C2215MPROV
ShutdownDC Levelfrom QX3001
FlybackPulse
To ShutdownPin 18, IC2200
<<Figure CB-19>>
supplies an E/W pincushion correction signal to IC3200, an op-amp in the deflection circuitry. This signal iscalculated by IC2200 to correct horizontal deflection that would otherwise give a �pincushion� appearancedue to the geometry of the CRT. IC3200 and its function is further described in the deflection circuitdescription. Note that it is only used in 32� and 36� CB receivers. Pincushion correction is wound into thedeflection yoke on the 27� receivers.
Two CB models, the IQB32B44W and the IQB36B44W, feature scan velocity modulation. Two coilslocated under the purity magnets on the CRT accomplish scan velocity modulation. These coils are con-trolled by the scan velocity modulator (SVM) board attached to the back of the CRT near the yoke. TheSVM receives fast-blanking and half-tone information from the microprocessor via the 4Q9 connector andvideo information from pin 15 of IC2200 via the 4X9 connector. These signals are processed to generate acurrent in the coils. The SVM varies this current to slow beam sweep at color transitions. The effectproduces a sharper video image in the CRT.
CB-22
CB CIRCUIT DESCRIPTIONS
Introduction
The CB chassis was developed to support CRTs ranging from 27� to 36�. Major component of the deflec-tion circuitry include IC2100, the vertical output IC; QX3203, the HOT (horizontal output transistor);TX3205, the horizontal drive transformer; and on 32� and 36� sets IC3200, the E/W pincushion correctionamplifier. Of course the yoke, connected at 3Y3, and the flyback (or sweep) transformer, TX3204, aremajor components as well.
Horizontal Drive
Horizontal drive (H-drive) enters the drive amplification circuitry through C3219 into the base of Q3201.This transistor and Q3202 amplify the h-drive using the +15VSW for power. H-drive then passes throughthe horizontal drive transformer for final wave shaping and voltage to current conversion. This modifiedhorizontal signal drives the HOT, QX3203. The HOT switches current flow in the primary winding of thesweep transformer, TX3204. Regulated B+ is applied at pin 3. Horizontal output also drives the horizontalscan signal in the yoke. Switching frequency of the HOT is 15.734 kHz.
1
3 4
5
6
TX3205
C3206
QX3203
LX3202
CX3212
C3204Q3202
C3203
R3205
R3204 CX3205
RX3207
+15VSW
R3203
C3202Q3201
C3201
R3202M
R3201M
C3219
CX3213PROV
DX3202
CX3257PROV D3203
RX3212
CX3258PROV
H-Drive fromPin 19, IC2200
Flyback Line
H-Output toFlyback & Yoke
<<Figure CB-20>>
Flyback Transformer
TX3204 uses HOT switching to generate high voltage. For this reason, the sweep transformer is oftenreferred to as the high-voltage (HV) transformer. HV should generally range between 29.4 and 31.2 kV.The flyback does not, however, exclusively develop high voltage. A number of secondary voltages arederived here as well. These should not be confused with the secondary voltages off the chopper, TX3401.The voltages developed off TX3204 are referred to as tertiary voltages in the power supply circuit descrip-tion.
Pin 2 of the sweep develops the +235V used to drive the cathodes at the CRT socket. This voltage isrectified and smoothed to DC by DX3201 and CX3208 and then applied to pin 4 of the 2F5 connector.Most of the secondary voltages are developed as DC in such a manner with the exception of pin 7�s fila-
CB-23
Deflection Controlment voltage, which is fed into pin 1 of the 2F5 connector, and pin 8�s ABL signal. For the filament�s part,since this voltage is needed only to heat the cathodes, it is not necessary that it be a DC voltage. ABL is fedto the video processor in order to regulate beam current.
CX3207PROV
RX3209
B+ DX3201
C3209
RX3208
+235V
CX3208
+14VDC
DX2104
C2112
C2111
RX2124
ABL
RX3217
RX3210PROV 1
2
3
4
+235 V
RX3211
CX3212
+35V
DX3252
CX3254 CX3253
CX3207A
RX3216
+33V
GND
G2
FOCUS
E
HV
TX3204 +14VSW
DX2105
C2114-14VDC
RX2125
-14VSW
RX3206
To FlybackLine Circuitry To HV Shut-
Down Circuit
To VideoOutput
2F5
6
9
7
5
8
3
2
1
H-Output
<<Figure CB-21>>
Pin 6 provides power for the +35V supply previously mentioned. RX3216 drops some of this voltage to+33VSW, which supplies the tuners. Pins 9 and 4 develop, correspondingly, a positive and negative14VDC. This ±14 volts powers the audio section. RX2125 and RX2124 serve as fusible resistors for the±14VSW supply to the vertical amplifier, IC2100.
Part Location Part # NotesIC2100 F-53864 All ModelsQX3203 F-53367 All ModelsTX3204 095-04438-04 All Models
<<Table CB-6>>
CB-24
CB CIRCUIT DESCRIPTIONSHigh Voltage Shutdown
The x-ray protection (high voltage shutdown) circuit uses the current from pin 6. DX3002 and CX3003convert this current to DC. The resulting voltage is applied to the resistor divider network in the emittercircuit of QX3002. Voltage applied to the base of this transistor remains constant because of the zenerdiode, ZDX3004. If HV reaches 35.7 kV (33.9 kV for 27� sets) DC applied to the emitter of QX3002will switch the transistor on. The resulting voltage across RX3002M will switch QX3001 on, attenuatingthe flyback signal on pin 18 of the video processor. If the signal is reduced to 1 Vp-p or less, IC2200 willcease production of H-drive and thereby shut down the set.
<<Figure CB-22>>
Vertical Amplification
The yoke receives vertical sweep drive from ICX2100, the vertical amplifier. This IC consists of a pump-up stage, a power amplifier, and thermal protection circuitry. The ±14VSW power the IC at pins 1 and 6.
DX3002
CX3002
CX3003
RX3005
RX3006
ZDX3004
RX3003
RX3004
RX3002M
DX3001RX3001M
RX3211
QX3002
RX3007
CX3001M
QX3001D2205
R2224M
R2222M
R2223MPROV
C2241M
C2214MPROV
C2215MPROV
From SweepTransformer
FlybackPulse
To ShutdownPin 18, IC2200
7
1
2
3
4
5
6
221-1410ICX2100
-
+AMP
Pump-Up
ThermalProtection
<<Figure CB-23>>
CB-25
Deflection ControlBoth positive and negative vertical ramp signals are required for operation. IC2200 supplies these to pins 4and 5 of the amp as non-inverting and inverting input. Pin 3 is an input for output stage VCC. Pin 7 is thepump-up output. Vertical output comes from pin 2 of the amp to pin 4 of the yoke connector. The otherend of the yoke provides feedback to pin 5 of the vertical amp and to the horizontal pincushion correctioncircuit.
<<Figure CB-24>>
The pump-up output from pin 7 feeds the CRT-protection circuitry. This circuitry provides a DC level topin 13 of IC6000, the microprocessor. The DC level at that pin should be between 3.6 and 5.1 volts. Ifthe voltage deviates from this range, the microprocessor will shutdown the set in 3 seconds. IC6000 willhave to be reset before the receiver can be turned on again. The purpose of this circuit is to prevent phos-phor burn or worse, the severing of the neck of the CRT. Pump-up current is rectified and smoothed byD2102 and C2108. R2109M and R2112M divide the resulting voltage before it passes through R2113Mto the micro. D2103 is a clamping diode.
D2102R2108M R2109M
C2108
D2103
R2112M
R2113M
+5VSBF
To Pin 13,IC6000
From Pin7, ICX2100
<<Figure CB-25>>
1
36
5
4
2
7 ICX2100
C2106R2101M
+14VSW-14VSW
C2103
CX2101
CX2102
D2101
R2102M
R2103M
CX2100 C2104
RX2105
CX2105
RX2106 RX2107 C2107
R2104M RX2110 RX2111 RX2114PROV
Vert-Output
Vert-Parabola
VDN, Pin14, IC2200
VDP, Pin13, IC2200
To CRTProtectionCircuit
32" & 36"ONLY
CB-26
CB CIRCUIT DESCRIPTIONSWidth and Geometry Correction
East/West pincushion correction is performed by circuitry built into 32� and 36� sets. The windings of theyokes used in the 27� CB chassis have this correction shaped into their design at assembly. Correction isnecessary on larger sets due to their geometry. As the CRT electron beam approaches the upper and lowerextremes of the screen, its horizontal scan lines sweep a wider length than they do in the middle of thescreen. DX3250, DX3251, CX3216, CX3252 and CX3256 act as a diode modulator circuit to limitcurrent in the horizontal yoke when the sweep is at the higher and lower edges of the screen. This diodemodulator relies on signals amplified by Q3250 and QX3251, and supplied by both the vertical yoke andthe video processor. Q3250 receives its power from the +35V derived at CX3253 off the flyback.IC3200 is an op-amp that boosts the signal from IC2200. It is powered by the +15VSW, and providesnot only pin-correction information, but also width control. Varying the DC level on the base of Q3250alters the overall screen width by changing the current through LX3201, the width coil.
R3252M
Q3250
R3255M
RX3256
R3253
QX3251
R3257M
TP3200
R3259
CX3251
LX3201
DX3250DX3251
CX3252CX3216
CX3256
C3217
H-Output from QX3203
LX3262
H Yoke
+35V
RX3215 CX3215
DX3203
RX3214 CX3218C3255
R3258
+15VSW
R3251M
W3259
W3202 LX3203
W3200
W3203
12345 6 7 8
IC3200
C3224
R3268R3267
E/W
R3266M
ABL
+15VSW
R3261M
R3262M
R3263M
R3264M
VerticalParabola
<<Figure CB-26>>
CB-27
Audio Development
Audio Processing
The CB chassis uses IC1400 to process audio. This IC features true MTS (Multi-channel TelevisionStereo) sound, dbx noise reduction, and SAP (second audio program) processing. Its I2C bus at pins 9 and10 allows adjustment for volume, balance, tone control, front surround sound, SAP switching, sourceselection, and stereo separation. IC1400 is powered by +9VSB at pin 24 and grounded at pins 22 and 11.
CB television receivers make use of at least 2 audio inputs to the audio processor. A third set of inputs isemployed on IQBxxB44W type models for audio boost purposes. A description of this process is below.The composite audio comes from a switch in the IF section through C1436 into pin 19. This allows selec-tion of composite audio from either the main or the PiP IF source. Refer to the IF circuit description for anexplanation of this switching. IC1400 processes this audio, separating SAP, left, and right audio. The leftand right channels are then output on pins 6 and 7. Alternately, the audio processor can use audio inputfrom an external source at pins 39 and 40.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
2425
36
26
27
28
29
30
31
32
33
34
35
37
38
39
40
41
42
43
44
45
46
47
48 BASSL2
TRE-R
TRE-L
SURRIN
SURROUT
LSOUT-R
LSOUT-L
NC
SDA
SCL
DGND
SAD
MAININ
MAINOUT
NC
PCINT1
PCINT2
PLINT
COMPIN
VGR
IREF
GND
SAPTC
VCC
BASSL1
BASSR2
BASSR1
SURRTC
TVOUT-L
TVOUT-R
AUX2-L
AUX2-R
AUX1-L
AUX1-R
VLTC
VLDC
VCAWGT
VCATC
VCAIN
VEOUT
VETC
VEWGT
VE
SAPIN
SAPOUT
NOISETC
STIN
SUBOUT
IC1400
C1401M
C1402M
C1404M
C1416
C1435MPROV
C1434MPROV
R1401 R1402
R1425M
C1421
C1420R1406M
C1418
C1436
C1413
R1404M
C1425
R1421M
R1422M
+9VSW
C1433MC1430
C1403M
C1406M
C1431M
C1409
C1410
R1409M
C1432
C1415
C1414
R1405M
C1417
C1427
C1426
C1428
C1419
C1422
C1424
R1407M
R1408M
* Not usedin all models
To AudioBoost Circuit *
SwitchedAudio In
CompositeAudio In FromIF Circuit
Clock &Data Lines
To Audio &External Amps
<<Figure CB-27>>
All audio input and output pins should meter 4.0 DC volts. Signal at pin 19 should have a strength of 245mVrms. All other audio inputs and outputs on IC1400 should scope at 490 mVrms. This includes the audioboost I/O described now.
CB-28
CB CIRCUIT DESCRIPTIONSAudio Boost
Those sets that have the audio boost feature output audio signal on pins 43 and 44 to IC1401. This IC ispowered by the ±14AUD. It strengthens the audio signal and returns it to pins 41 and 42 of the audioprocessor. From here, the boosted signal is output from IC1400 on pins 6 and 7.
OUT1 OUT4
-IN1 -IN4
+IN1 +IN4
V+ V-
+IN2 +IN3
-IN2 -IN3
OUT2 OUT3
10
9
87
6
14
13
12
11
5
4
3
2
1
IC1401
R1490M
R1491M
R1489M
C1484
R1488M
-14AUD
C1482M
R1486M
R1487M
C1479 C1478M
R1484M
R1485M
R1482M
R1483M
R1492M
C1483
C1477M
C1476M
R1477M
R1481M
R1478M
R1479M
R1480
C1475
R1475M
R1493M
R1476M
C1474MC1473
+14AUD
C1481C1480M
C1472M
R1474M
C1471M
R1472M
R1473M
R1471M
43
41
42
44TVOUT-RIC1400AUX2-R
AUX2-LIC1400TVOUT-L
<<Figure CB-28>>
Audio Amplification
CB receivers employ two 8-ohm, 7-Watt speakers. These are driven by IC804, the stereo audio amplifier.Although the audio amp is capable of driving 10-Watt speakers, the supply voltage has been reduced from+36 volts DC to +22 volts. Normal gain of this IC is 42 dB. In order to drive the speakers at 5 Watts, asignal strength of only 50 mVrms is necessary. Such a low strength signal is susceptible to noise interfer-ence, so the gain is reduced to 32 dB by negative feedback from the output in order to allow for an in-creased signal strength of 142 mVrms. R868 and R869 accomplish this reduction for the right channel andR858 and R859 do so for the left channel. The output level from the amplifier is 425 mVrms. Cut-offfrequency is 14.3 kHz and is determined for right and left channels by C865M and C855M respectively.
IC Location Part # NotesIC803 221-00170 All ModelsIC804 F-53765 All ModelsIC1400 221-01127 All ModelsIC1401 221-00188 IQB27B44W
<<Table CB-7>>
CB-29
Audio DevelopmentThe +22VSB is supplied to pin 10. Pins 4, 9, and 12 are grounds for the amp. Pins 5 and 2 input left andright (L/R) channel audio fed through C851 and C861, which eliminate any DC accompanying the signal.Pin 3 provides a reference voltage. L/R output comes from pins 7 and 11. Pin 8 is a line that, upon receiv-ing a switching DC level from the micro, mutes the speakers. This occurs when the user selects the speakercutoff option.
External Audio Output
External variable monitor output jacks are included on the CB jack-pack. Their signal is provided byIC803, a dual op-amp that receives L/R from IC1400 into pins 3 and 5. This amp IC is powered by the±14AUD at pins 8 and 4. Audio output to the variable audio output jacks comes from pins 1 and 7. Theop-amp provides a net gain of 12 dB.
1
2
5
64 9 12
113 10
8 7
OUTR OUTL
VCC
GND
VREF-INR
+INR
-INL
+INLMUTE
GND
GND
IC804
1
2
3
4C854
C864
C853
C863
R853
R863
C852
R859
R858
R870
C847PROV
Mute
C862
+22VSB
CX841C842
C843
R868
R869
R861M R851M
R862M R852M
6 7
C861
C851
C865M C855M
C822
C832
1
2
3
4 5
6
7
8
IC803
R826M R836M
+14AUD
-14AUD
C850 C844M
C857 C856M
R823M
R833M
R822M
C823
R832M
R824M
C833
R834M
R825
R835
L & R Outfrom Pins6 & 7, IC1400
9S4
27 2625
Part of J1,Jack Pack
VariableMonitorOut-Right
VariableMonitorOut-Left
To TVSpeakers
<<Figure CB-29>>
CB-30
CB TROUBLESHOOTINGStart
1. No Power
Plug receiverinto AC source.
ReplaceFX3401.
ReplaceFX3402.
Check RX3423.Replace TX3401 if
necessary.
Check DX3406,DX3407, CX3410.Replace ICX3412
if necessary
ReplaceICX3402.
Yes
No
No
No
No
No
No
No
Yes
YesYes
Yes
Yes
Yes
ReplaceIC6000.
Check +15VSBsupply at CX3428.Check ICX3401.
Check Q3402 &Q3405.
ReplaceIC2200.
Refer to shutdowntroubleshooting.
No
No
No
No
Yes
Yes
Yes
Yes
Is ACconnected?
Does FX3401conduct?
Is B+ present atCX3420?
Does FX3402conduct?
Is pin 3,ICX3412
switching?
Is +12VSBpresent across
CX3427?
Is +5VSBpresent across
C3426?
Does pin 32,IC6000 emit aDC pulse at
startup?
Is +9VSBpresent across
C3429?
Is +9VSWpresent across
CX3436?
Is Horz & Vertdrive present onpins 13, 14, 19,
IC2200?
Are ICX3406and ICX3403
OK?No
Yes
ReplaceICX3403,
ICX3406 asnecessary.
CB-31
Flowcharts2. Shutdown
Start
Does the setpower up formore than 2seconds?
Does the Vp-plevel at pin 18,IC2200 stay
below 1.0 volts?
Checkmicroprocessor
ciruitry.
No
YesCheck HV-
shutdown circuit,sweep
transformer.
Does the setshutdown afterjust 3 seconds?
Check IC2100 &CRT protection
circuit.
Yes
Yes
No
No
Is B+ running at aconstant DC
level?
ReplaceICX3412.
No
Yes
CB-32
CB TROUBLESHOOTING3. No Tuning Start
Are all tunervoltages
present? (Referto schematics.)
Check tunerpower supplies.
Is IF present atpin 11, WT1200?
Does changingthe tuner fix the
problem?
Check clock anddata lines.
Replace IC6000if clock & data
lines OK.
Is IF present atpins 5, 6,IC1200?
Check IF line.Replace U1200
if necessary.
Is IF present atpin 17, IC1200?
Check IC1200power supplies.Replace IC1200
if necessary.
Refer to No Audio and NoVideo Troubleshooting.
Yes
No
No
No No
No
Yes
Yes
YesThis procedure may beapplied to the 2nd tuner
section as well.
CB-33
Flowcharts
4. No Video Start
Is raster presenton the screen?
Is 1.07 kVp-psignal present on
collector ofHOT?
Is regulated B+present at pin 3
of TX3204?
Check powersupply.
Check TX3204for high voltage.
Check HOT andH-drive circuit.
Is there luma atpin 4, IC2200?
Is luma missingat pin 34,IC2900?
Is RGB outputpresent at pins
22 - 24, IC2200?Replace IC2200.
Is RGB presentat pins 1, 2, 3,
connector 5C2?
Check Q2205,2206, 2207.
Is the SETUPjumper open?
Is +235 VDCpresent across
C5100?Check TX3204.
Check G2adjustment.
Yes
No
Yes Yes
Yes
Yes
Yes
Yes
Yes
No No
No
No
No
No
No
Remove setupjumper.
Is compositevideo missing atpin 36, IC2900?
Check Q2901and +9VSW
source.
No
Yes
NoCheck DL2400or IC2400 and
comb-filtercircuitry.
Is there video IFpresent at pin50, IC2900?
Yes
Check video IFline, Q1200, pin
21, IC1200
No
Yes
Replace IC2900.
CB-34
CB TROUBLESHOOTING
Check audiopower supply.
Is +22VSBpresent on pin
10, IC804?
Start
Does DC levelchange at pin 14,
IC6000, whenspeaker cut-off is
toggled?
Is L/R channelaudio missing atpins 2, 5, IC804?
Is L/R channelaudio missing at
pins 6, 7,IC1400?
Is compositeaudio missing at
pin 19 ofIC1400?
Is compositeaudio present atpin 1, IC1200 (or
IC1250)?
Replace IC6000.
Replace IC804.
Check IC1400VCC. If it is
present, replaceIC1400.
Check L/Rchannel lines.
5. No Audio
Yes
No
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No Replace IFprocessor.
Check Q1290,1291, 1292, &1293. Replaceas necessary.