The problem was a faulty OP Amp type 4741-5. Unfortunately that chip was discontinued and would have to be ordered. You can use a LM324 instead. Shouldn't be that hard to find which one's bad. Very cheap fix. Good Luck!
I just got set of Valley Peoples Gain Brain II compressors and one of them seems to have similar problem that you had earlier. Did you find solution for the problem? Manuals?
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