MC202 problem

[Daniel Araya]

Hi!

Sorry, Rob, that didn't work. But I understand why one should change them, 
some of them were just about to break!

Do anyone know the inner workings of the 202's electronics? Especially the 
AD/DA section...  HELP!


/Daniel

At 17:50 2000-11-09 -0500, you wrote:
>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!!!)
> >