MC202 problem

[Daniel Araya]

Hi!

My Roland MC202 just broke down!

When i power it on it locks up in some strange mode (displaying "-1 
-     1"  in the display) and none of the buttons work. The analog part 
works fine and I can play it from an external keyboard but the notes enterd 
doesn't show up on the display and the "glissando"-effect is gone.
Once in a while I get some response from the startbutton which starts the 
machine in "realtime"-mode, but you still can't enter notes into memory.
I think these faults are due to me hooking it up to a broken CSQ100 who 
apparently outputted an unkown (high) voltage at its gate and cv outputs.



I have the schematics and i think i understand the general idea but it's a 
bit complex...

What is a "NJM 082DR" ? Is it a TL082?
It is the A/D comparator and i think its funktion is somewhat similar to 
the quantizer in the Oberheim sequencer. I guess the D/A outputs som kind 
of reference waveform that is compared to the external cv-signal...has 
anyone got any idea of the shape of this waveform? On my 202 i get a wave 
with only like 3 different levels....that seems wrong...
And the comparator outputs a steady pulse regardless of what i feed to the 
cv in.

Is the processor fried or is it something else? What can cause it to lock up?
Anyone with experience in repairing 202's that can help me?


/Daniel, Sweden   (heeeelp!!!)