One of my main pieces of advice to anyone learning to fix vintage synths is to never underestimate the likelihood that whatever problem your synth has is just because of cold solder joints. This one had a dead master oscillator and after testing and scoping all around it and comparing my findings to another Juno 60 that’s here, it turned out to just be because of cold solder joints on the inductor. I learn this lesson over and over but I don’t really learn: when troubleshooting a problem whose source isn’t clear, you might as well always reflow first. I’ve learned it with reference to Moogs but forget to remember it with reference to Japanese synths.
Service tips: Almost every Juno 60 I’ve worked on has had at least one slider with what I think of as a “snag,” a point at which it gets stuck, which you have to force it past. This is what a snagged slider looks like when you take it apart. The piece in the foreground should be flat. You must flatten it out as much as possible so it’s a nice smooth rectangle again, clean everything and put it back together. To give the slider a good feel, it’s important to lubricate the underside of the topmost surface of the slider case as well as the track.
Work Done: repaired dead master oscillator, cleaned and lubricated all sliders and took apart and repaired several snagged sliders, updated power supply as usual, reflowed all jacks (standard procedure with all Junos now) because mono chorus mix was not working (very common), replaced a broken-off toggle switch, calibrated.