OBERHEIM SYNTH

HELP!! im having problems with my oberheim matrix 6.

when it came to me less than half of the presets worked, the rest were just noise. so i reloaded the sounds from the original audio tape and to my absolute joy/astonishment it fixed it 100%.
but now about 2 months later, I tried turning it on after not using it for about a week, and it wont even light up(at first). so i tried turning it off and on quickly. when i do that the display lights up and reads either "HHHHHHHHH","PWPPPPPPP","@@@@@@@@@" weird letter combinations like that(3 different combos consistently)i cant find if those are some kind of error code or not anywhere on the web.
Its been plugged into a very good power conditioner since i've had it, so im not betting on a power surge as the culprit. i know a little bit about circuits and electronics, nothing looks burnt out on the board, nothing smells burnt. i removed every IC i could, cleaned and reseated it, but still same thing as before(on/off slowly = nothing, on/off quickly = letter combos)
any way im just curious if any one has ever seen or heard of this before, and what it might possibly be, i couldn't find a single thing about it online!
i love this synth, it have become my favorite one in the past couple of months, i would hate to see it die.