MC202 problem

[rob]

First thing I would have a look at is the wires between the boards, namely
that cheap white multiwire crap.. I have had those go bad in a 606, 101,
and a couple of other nameless consumer electronics. ;)

Analog section works fine, but the sequencer, buttons, etc all do wierd
things.. Same symptoms like mine all had.

replace all the wires between the switchboard and the analog section and
whatever else and you will probably find that it suddenly starts working
again.

Rob


----------
> From: Daniel Araya <daniel.araya at mail.bip.net>
> To: synth-diy at node12b53.a2000.nl
> Subject: MC202 problem
> Date: Wednesday, November 08, 2000 1:12 PM
> 
> 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!!!)
>