This Roland JP8000 synthesizer came in with no audio output on the main jacks. Headphone worked, but a bit low level. I did a quick search on the internet and found two common problems, both based on bad caps. Either the electrolytic capacitors on the jack board are bad, or one one the mainboard. Since the headphone was working I concentrated on the mainboard. I figured out that the electrolytic capacitor C219 on the main board that sits in the audio mute (reset/power up) circuit and was bad.
After removing I could clearly see the electrolyte causing corrosion.
I removed the old SMD electrolytic capacitor, cleaned the board and replaced it by a new one. Works fine. Quick job, happy customer. Here are the pictures I have taken during the repair (as always for my own purposes, but I share these with you guys).