Hard to pass audio when cold

[Stefan Boman]

Trying to fix some stuff myself before calling my tech guy.
I have a 4KE that has one channel that won't pass audio in REC mode on tape return(VCA to mon) when cold.
Mix is fine. And it usually goes away after 15 min or so.
Before that it's quiet. Unless I hit it really hard. Then it leaks thru, but disappeares when it gets lower.
Same thing if I crank the eq.

Any ideas on where to start?
Grateful for clues!

[Dan Korneff]

Could be a cap... or a switch (maybe phase switch).
Do you have an extender card? I would swap out the amplifier card with a good channel and see if that fixes the issue. If so, recap, re-chip, and record!

[Artur D'Assumpção]

Hi,

I have had similar problem in the past, in other sections of the console, and that symptom was always related to a transistor in the audio path. Somehow when it was cold...it was passing little to none signal, when when it heated it started to entering its nominal operation.

I would try to pinpoint on which exact section the problem is with some basic signal flow troubleshooting and then put the channel on an extender and pinpoint exactly which component (transistor?) is the culprit.

Good hunting!

cheers,

Artur

[Stefan Boman]

Thanks guys!

Guess I'll go hunting

[xmax]

I have seen the same thing with the square 2.2uf .1% caps.