[sdiy] Roland MKS-70 problem - need advice

[Gil W.]

I have a MKS-70 which suddenly started to act strange.
First I powered it up and all the display characters
lite up. I managed to solve that after replacing the
electrolytics and two ICs on the display board but
other problems remaind (I don't know if they occured
at the same time the display problem rised up or as a
result of servicing the unit... however it worked
perfect till then). The A block hasn't made any sound,
or played corrupt, low distorted sound. Also sometimes
when I plugged a TRS into the headphone jack the unit
seemed to reset (got back to the welcome screen and
stuck there). I managed to solve the board A issue
after finding the CPU (8031) was not functioning
correctly and replaced it, successfuly (now it played
OK again) but the reset problems has remained, as well
as the system hangs up sometimes when I edit tones, or
even boot up showning parts of one or two characters
(although it happened only once). I replaced the
battery if that makes any difference and reloaded the
unit with factory presets.

I did find that the unreg. voltage going directly from
the main trandformer, and which by the schematics
should be +7v, is 12.5v when the powersupply is not
connected to the rest of the unit, and 10v when it
does. Could that be the problem ?

Any help is much appreciated !


		
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