I've been testing some ISA sound cards I have bought over time and encountered weird problem with two of them - Sound Blaster Pro 2 (CT1600) and Sound Blater 32 (CT3620). Both work well, apart from the fact they produce sound only in left channel. I've tried to clean the SPK OUT connectors with IPA but the problem persists. Visually both cards look good, if a little dusty. No stratches or burns.

Did any of you encoutered similar problem? Did you solve it somehow? Where to look? Thanks!

EDIT: With some more digging I've found this thread: SB16 volume far too low and only one channel. I'll try to replace some caps and see if it solves the problem.