Two of my A-131 log VCAs from 1999 have the same problem:
The initial gain control (top pot) barely works at all. I have swapped
the modules for other working VCAs to isolate the problem to the
module itself and not the bus or rack. I even swapped the IC1 and IC3
from one to another without any luck.

The modules are the CEM version I believe, and there is no sign of any
component having failed. All the other features work, but when you
apply a CV to CV1-in or CV2-in then the initial gain control does have
an effect.

I am wondering whether this is a common problem with the CEM chip or
if anybody else has had similar problems.

sean