[sdiy] Roland MKS-70 problem - need advice

[Bob Weigel]

Hmm..it sounds like maybe there's an intermittent connection 
somewhere..but likely voltage you are observing at the unregulated test 
point is irrelevant.  Schematics post sometimes a minimum fully loaded 
voltage or something.  I often see variations from what I read in a 
diagram to what actually appears in an unregulated voltage line. -Bob

Gil W. wrote:

>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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