THE CORRELATION BETWEEN TRUE COXTACT POTENTIAL AND VACUUM TUBE PROCESSING AND CHARACTERISTICS

Eugene Maloney (Raytheon Mfg. Company) Many of t he v a r i a b l e s i n t u b e making such a9 parts, processing, regular and

accelerated burning are discussed with reference to t h e i r e f f e c t on t rue contac t potential. The re ta rd ing f ie ld t echnique has been used as the method of measuring contact po ten t i a l and a l l measurements we're made on the 6AK5. Various ligh$ing schedules on the exhaust machine were investigated, and t h e r e su l t s r epor t ed . quantitative evaluation of bombing temperature influence on con tac t po ten t i a l was made. Contact potent ia l was checked after each of t he va r ious s t eps i n t he ag ing Bchedule. A p l o t of true contac t po ten t ia l vs time i s shown for tubes which were burned 46 hours. The oor re la t ion between t rue contac t po ten t ia l and oharac te r i s t ics is discussed .

THERMAL EFFECTS I N VACWM TUBES Irving E . Levy (Raytheon Mfg. Company)

i s t i c s and l i fe . Heater temperatures range from l l O O ° C t o 12OOOC. Cathode tem- peratures range from 700% to 8OO0C (optical pyrometer). For each tube type there i a an optimum heater and cathode temperature. Excessive heater and cathode tempera- tures cause leakage, shorts, sublimation, gr id emission a.nd poor l i f e . Cathode temperatures which are too low r e s u l t i n more vulnerabi l i ty to ca thode po isoning and low emission. Grid temperatures, which range from 225OC t o 50O0C, are mostly controlled by cathode temperatures. Excessive grid temperatures cause grid emission, gas, and poor l i f e . Plate temperatures range from 200% t o 5OO0C. High plate tem- perature ope ra t ion w i l l r e su l t i n gas and cathode poisoning. With r e f e r e n c e t o the tube envelope, bulb temperatures range from 85% t o 235OC. Electrolysi,s, gas, leakage and poor l i f e are t h e r e s u l t s of bulbs which run too ho t . Ef f ic ien t sh ie ld ing has been found t o minimize t h e e f f e c t s of excessive bulb temperatures. Quantitative thermocouple techniques have been used to evaluate temperatures resul t ing f rom var i - ations i n materials, procesaing;deeign changes and tube operation. More e f fec t ive aontrol i s provided over temperature f luc<uations, and reliabil i ty i s increased.

Vacuum tube component temperatures play an important part i n tube character-

MICROPHONIC REDUCTION I N FILAMENTARY TUBES Vladimir Kenn (Raytheon Mfg. Company)

This paper concerns i tself with t h e problem of reducing the microphonic noise in filamentary type tubes. The difference, a s it ,a f fec ts microphoniam, between indirectly heated cathode tubes and filamentary tubes is discussed.

The problem of redesigning t h e tube s t ruc ture i s a t tacked by inves t iga t ing the . nature of the interelectrode motion and the revl t ing microphonic output . This i s done by v ibra t ing the tube in a spec ia l ly des igned v ibra tor , The tube i s subjeoted t o two different kinds of excitation, and t h e microphonic output i s analyzed by two different methods. In addi t ion a method i s discussed for invest igat ing the mechani- Col resonant frequency of the f i lament and i t s mechanical "Q". The microphonio W t p u t of the improved tube i s shown t o be more than 20 db lower than the regular Produotion fi lamentarg type tube, and l o c a t e d i n a more advantageous portion of t he frequency spotrum

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