I had my Juno-G “fade away” while playing in the basement with headphones on. I tried another set of phones, still no sound. Just one moment the sound was present, the next moment it was gone. I only tinker at the house so the Juno never leaves my home nor does it get moved. I noticed wiggling the jack, the sound would get louder for a moment but not fix it. I plugged the keyboard into a bass amp. the sound was VERY low even with the volume at 75%. I did the wiggle of the output and it got VERY loud. My first thought was a cold solder joint and I took the Jack board out and re soldered the jacks. It didn’t help. I noticed one foam cushion was very yellowed compared to the others. I picked at it a little but then pushed it back down. I next tried cleaning my connector jacks, it also did not help. I suspected the coupling capacitors on the Jack board and located the schematics online.
I knew the jack cleaning DID NOT HELP, BUT when I wiggled the cable in the jack, it would sometimes get louder so maybe something weird was going on with physical flexing / movement of the PCB. And not the caps. I started checking caps anyways and found the 100uf 16v and 10uf 16v surface mount caps checked “questionable”. I replaced a few in critical areas (headphone circuit and output A jacks). I tested again, FULL VOLUME! HOT DOG! After a few moments, audio faded away again, came back then faded away again. Something was SCREWY!
I remembered the crusty foam. This foam had turned brittle and dark yellow while other foam parts on the back of the jack board were soft, white and very pliable. I removed this foam pad as it didn’t seem to have much purpose in the spot as there is no frame under it. (I believe the Jack board might be used by Roland in SEVERAL models so they simply stick the foam pad on to meet the requirements of the production run of several units.) I used a small amount of acetone on a swab to clean the VERY brittle and dried adhesive from around the pins. for good measure, I also re-soldered the pins of CN-2. The schematic shown this connection carries the audio from the rest of the synth. I reassembled and tested.
My JUNO-G is now fully operational again. Headphones, Line outs A and B are all working and NO sound fades. I even performed a 24 (leave it on) burn in test. The next day, Mr. Juno G played with out any audio issues. It has now been over a week of power on/ power off cycles and the audio has no issues. If I had to do it over again, I would have went with my instinct and cleaned that dried out yellowed cushion pad off first.
I’m not 100% sure if it was the crusty glue conducting OR possibly one of the few caps I replaced. They were non-HB series Panny caps that lead me to believe the high ESR may have been the issue too.
Just wanted to share this as maybe it will help someone else…
OH my Juno has FW 2.01 and the display replacement so hopefully it is good to go for a spell.