Etherwave Standard Volume Issue

Hello. A friend of mine has an Etherwave Standard that was recently knocked off a table (possibly while the AC adapter was connected). When he tested it afterwards, it appeared that it was no longer outputting anything. Then he noticed that he could hear the proper pitch very quietly if he cranked up his amp.

When he contacted Moog about the issue, they suggested tuning the volume circuit by adjusting L11, but this appeared to have no effect.

We've tried a few traces but I'm not exactly sure what to look for. If anyone has any suggestions, I'll try them out.

Thanks!

UPDATE: Diode D1 was dead conducting both ways. Everything is fixed now. I've seen similar problems posted online before, so I hope this information helps.