A customer sent me a JV-90 to repair. Customer states patch data corruption while in use which lead to weird sound all over the place. Customer also asked to replace all tact switches.
Upon inspection, I found data card board to have black stains. Further tests shows that this black stuff is corrosive and the vias has been etched away, a bunch of signals now does not connect to main board, including reset. Data card is not functional. This is most likely the reason why the data is corrupted while in use: the chip was never reset and is probably putting garbage into the bus.
The right hand side panel board has a large crack which has been repaired before. I also found some cold solder joints on the main board. Pulling the PSU caps shows they are still usable but have some degradation.
For the main board, I reflowed all QFP solder joints and all connectors.
For the data card board, I fixed all vias by scratching away the solder mask and connect both side of the via with wire.
For the PSU board, I replaced all electrolytic capacitors and applied thermal grease when re-installing the board.
I re-did the repair on right panel board, and replaced all tact switches.
After re-assembling the synth, I tested everything using test mode, including the SR-JV80 expansion and Data card, use my own products.
