[sdiy] strange analog problem (mixer console)

[harrybissell]

Ahhh now I get the whole story...

Probably the trouble is that a solder joint on a resistor is bad (open) and
a capacitor is charging to a point where the circuit no longer functions...
the big blast of electricity probably resets that cap (which slowly charges
up again)

This happens all the time in opamp positive inputs which do not have a DC
bias path...  the input capacitor charges up with the bias current and the signal
just craps out.

Look for that. Fixing the solder joints would do it by restoring the proper
biases...

H^) harry

Ingo Debus wrote:

> Nils Pipenbrinck wrote:
> > 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.
>
> I had a similar problem with my old stereo amp. This was a kit I had
> assembled when I had been quite young and not good at all at
> soldering. Usually I had just to turn up the volume for a moment to
> fix the problem. One day I got tired of this and I resoldered
> everything. The amp was full of bad solder joints. Since then it
> worked fine. AFAIR I didn't replace any component.
>
> I have no idea why a bad solder joint can be made conductive again for
> a while with a higher voltage or current. Anyone?
>
> Ingo