> From: wasteking1@...
>
> we are onto something here----
> i turned R17 trimpot clockwise about 45 degrees clockwise
> and the led went on-- the control panel returned to normal
> Led patterns---- i went another 10 degrees and now when i
> start it up it flashes the bulk of the Leds once , and
> then stabilizes with the normal ON pattern , and controls
> work and the unit plays normally (so it seems) . -- i then
> measured the voltage as you described --it was maybe 4.8v
> so i turned R9 up till it neared 5v , then i was able to
> turn R17 down some --
> now the same '10degrees past Led lighting up ' was an
> increase of only about 30 degrees of clockwise rotation .
> is there a 'balance between these trim pots? can they be set
> too high? or is it 'fine'.....

One sets the voltage, the other sets the threshold at which the CPU is allowed to operate. The ideal, as I said, is for the DC OK line to turn on when the supply is about 4.8V. The easiest way to do that is to use the other trimmer to set the voltage to 4.8V, adjust the DC OK trimmer to the point where the light just turns on, then set the voltage to 5V. That will give you 0.2V of margin.

> Does this mean the transformer or another part of the power
> supply system is damaged? it seems like a big adjustment
> since it was fine a half hour before and my other keyboard
> that was plugged in at the same time thru the same power
> strip ( a DSI Polyevolver) seems to have has some memory
> corruption that seems like some internal electronic damage
> and the factory tech guy has suggested i send it in to them
> for repairs.

The transformer is unlikely to be bothered by much of anything. It's possible a power surge damaged something, but it's also possible that years of very slow drift just happened to reach the threshold at the same time something unrelated happened to your other instrument.

--

Ciao, Paul D. DeRocco
Paul mailto:pderocco@...