hello!
I recently bought an old Alesis Ion that had some issues. Since buying, I have upgraded the OS, cleaned the synth inside and out, and cleaned key contacts of four dead keys (the top four keys of the keybed).
The key contacts didn’t seem dirty, which was what I expected to find initially. I have read it may be worth replacing the contact strip. I also wonder if perhaps the ribbon connector has a minor issue and should be replaced?
the main clue I have is that only the top four keys are dead. Also, the pitch wheel seems to have a mind of its own I’ve recalibrated it in diagnostic mode, and oiled the spring slightly, but I can’t seem to fix it. Anyone have a fix for that issue?
thanks all!
I would remove the rubber contact strips on the high contact board and check the continuity of the trace data lines and verify they are not broken using a multi-meter point to point also looking for corrosion of the trace lines which can be caused by a spill on to the board.
Do you have the service manual for it?
It details the wiring of everything in the synth. Might give you some clues
FYI: the Ion service manual is available with a Google search.
Regarding the pitch wheel, make sure the POT_REF voltage (see schematic) is not noisy.
I repaired a bad Ion last year where Q19 (transistor) that supplies POT_REF voltage was bad.
The MOD 1/2 and Pitch Bend are identical 5K pots - you may try swapping them (just move the center pin (wiper) wires of MOD2 and Pitch Bend as a test). Maybe replace the pot, if cleaning cannot fix.