I bought a faulty DX7IIFD with hopes of repairing its problems. First on the list is a group of twelve keys that don’t play (middle C# up to C). The traces on the keyboard’s circuit board appear clean with no breaks. I have not disassembled the keyboard assembly itself to inspect contacts, etc. (Removing and replacing all the keys is a little daunting.
Additional problems are left channel only in headphone jack, volume slider doesn’t function in the low range, and the floppy drive transport doesn’t let disks “thunk” down and seat properly.