After finishing the setup for my CP4500 (which was after some issues that had me reordering the VCA chips and some op-amps to replace the ones I think I damaged) I was able to start using my CP4500. Yesterday I was mixing with it just fine - both channels were working in my Radial 500 series chassis just fine.

Today I turned it on to use it and it was mostly working, except that randomly the compression would kick in hard and release - like the needle would jump all the way to max and the volume would crash before relaxing again. This kind of thing happened before, which was why I ordered some more op-amps. I diagnosed that problem during setup of the first channel by seeing that TP4 was -16V with no input, and then when I swapped the op-amp with a new one from the other channel it worked fine.

So before I start taking everything apart and trying to debug I thought I'd ask here the best way to diagnose what's going on. I don't have the extender cables so I'll be debugging inside my chassis, so hopefully I can get some targeted debugging help. Thanks!