[Collins] VOX Problem

[Dr. Gerald N. Johnson, electrical engineer]

Grid emission in the 6U8. Leaky C119. Leaky C118. Presuming the
capacitors around the VOX rectifier are labeled the same in the S3 as
the S1. C119 bypasses pin 5 of the 6AL5 to the switched +275. Or inserts
a locking transient when the relay closes. C118 couples the plate of the
VOX amp to the VOX rectifier pin 2. Leakage in either will drive the
relay tube a little positive. Less leakage in both will do it too, as
will grid emission in the 6U8 triode section. The circuit impedance is
very high so capacitors need to have leakage resistances on the order of
1000 megohms. The original black beauties never could do that. Orange
drops can.

73, Jerry, K0CQ, Technical Advisor to the CRA

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.