I bought a Nobels SST-1 pedal new back in 1988. (RockMan clone) Have been using ever since. Parts are all original. Lately the chorus level is low. Adjusting the pot goes from there to not there. There are no other problems. This thing looks like it would require care when disassembling, so I would like to get a trouble shooting guide first. From my schematic I suspect C306. Anyone see any other part that may be at fault? I welcome all suggestions.
(https://i.postimg.cc/QVRNDS1J/SST1-IO.png) (https://postimg.cc/QVRNDS1J)
(https://i.postimg.cc/N5msjTxq/SST1-CD.png) (https://postimg.cc/N5msjTxq)
Have you got a better schematic please? That one's everso small.
Oh, nevermind, I found it on Electrotanya:
https://elektrotanya.com/nobels_sst1_sch.pdf/download.html
From the schematic, it looks like the only pot associated with the chorus section is an LFO depth pot, not a level, so it's no wonder twiddling the knob doesn't change the level problem much. More intense chorus will perceptually sound a bit "more", but it's not actually getting louder.
You might be right about C306, but it's far from the only thing in the chorus signal path. I'd get an audio probe and check C306 first. If the delayed signal is strong there (you should hear a solid signal with vibrato, but not chorus since there's no dry signal) then perhaps the problem is further along in the the filter. Test the filter output at pin 7 of IC202B to check that. After that, it could simply be that the switch contacts are corroded or old and dirty. I also notice that the dry/wet mix is completely different between the right and left sides, so have a listen to both.
If I had to guess, I'd go for the switch. In my experience mechanical failures are much more common than electronic ones. But on an old gizmo like this, I guess all bets are off.