[sdiy] strange analog problem (mixer console)

[Nils Pipenbrinck]

My Behringer mixer - after several years of duty - has some strange problems
lately.

I just wonder if anyone of you have experienced a similar effect or knows
what's wrong.


When I turn it on the right channel is dead, regardless which input I use. I
can measure the signal, but it's only a tad higher than the usual noise
floor and distorted. The pots, faders and switches are fine.

However, I can "activate" the right channel again by running a hot signal
into it (9V battery does this job). It makes "plopp" and then the right
channel comes to life again. It'll also stay alive as long as some signal is
present (usual audio, not the 9V). I'm still happy with the mixer. After
resurection it sounds as it always did. Just the "kick in the butt"
procedure is anoying.

Btw, if I stop using it for a while (no signal at the inputs, but chords
connected) the right channel will go dead again.

Does anyone know what could be the cause of this? My only guess is a heavy
dc offset between the devices which cause the opamps to latchup, but that
would not explain why only he right channel is dead, and why the resurection
works.

  Thanks,
		Nils