> I did a search of the database and didn't see anything describing this.
>
> I just got a used a-132 dual voltage controlled amplifier. The
> upper VCA is functioning properly. The lower VCA is not working
> properly. It has a very low output and "thumps" or "pops" when
> it opens/closes no matter what signal I use to open it. There's
> a very large difference in the upper and lower channels.
>
> I was passing audio through it and opening it with an LFO. The
> upper channel behaves as expected but the lower does not with the
> same signals.
>
> I also have another A-132 and both channels function very similar
> and are similar to the upper channel on the problematic module.
>
> Anyone have any ideas where to look for the problem

From the distance it's difficult to find out what's wrong. If you are
experienced with electronics you could swap the integrated circuits of the
upper and lower section to find out if one of the integrated circuits is
defective. Maybe the module has to be readjusted (nothing but minimizing the
"plop" input connected to GND and e.g. an ADSR as CV).

Best wishes
Dieter Doepfer