This vintage compressor/limiter had lost it’s punch and other channel was making noise even without input signal.
Full electrolytic recap brought the punch back but noise was still there. Tried swapping the output cards between the channels but noise persisted on the same one so problem wasn’t in the cards. Tracing the noise with my oscilloscope I found it was one of the ic’s in the output section that was crapping out. Replaced that and everything was purrrfect :)