Identifying bad capacitors on the EX90 mic input circuitry causing non-working

microphones

In EX90s manufactured prior to week 41 2012, a common problem is that the microphone stops

working. This is in most cases caused by capacitors breaking in the A15V or A5V power circuits

that are fed to the audio input circuitry. The following pictures illustrate steps to be taken if

attempting to fix this problem.

Step 1. Remove the panel covering the mainboard. Also remove EMC shielding

foam if present.

EMC shielding

foam

Step 2. Power up the mainboard and observe the green LEDs on the bottom left

side of the mainboard light up. If all LEDs light up, the unit audio input power

should be ok, and no further actions should be taken. Every LED represents a

power input and if the +A15V , -A15V or A5V LED is not lit, this will affect the

audio circuit and cause not audio. In the below picture, the +A15V is not lit, hence

the problem is located somewhere along the +A15V power circuit. If A5V is not lit,

got to step 6.

Step 3. Unplug the power and disconnect the USB/audio input board by pulling

out the FPCB located to the bottom right on the main board. Replug the power

and check if all LEDs light up. If they do, the problem is located on the USB/audio

input board located on the bottom right. If the LED does still not light up, the

problem is on the mainboard itself, proceed to step 5.

FPCB

Step 4. Disconnect the USB/audio input board. Replace the broken capacitor C60,

C59 , C61, or C62 (located on the other side of the board) as shown in the picture.

The capacitor will typically look damaged if broken. If replaced use a CASE-D 47uF-

35V capacitor.

C60 C59

C61

Step 5. Check capacitors along the +A15 or A15V path. In this case C2175 was

found to be broken. Removing this fixed the issue.

C2175,

4u7-25V 0805

Step 6. If the A5V LED is not lit on the front side of the mainboard, remove the

capacitor C3315 located at the bottom of the back side of the mainboard. This

capacitor should be replaced by a 22uF capacitor with minimum 10V rating.

Mainboard, back side.