Vintage Synth Repair

Hi moe
thought you would have, just a good place to start.

There are two main boards in the unit. You can disconnect DM2 (the sound generating board with the 2 M3 chips on it) from the main controller DM1 board by unplugging the ribbon cable.

You should be able to power on the unit and play it as a Midi controller if the DM1 board is OK.

If you can, then look at the DM2 board.
The DM2 to DM1 connection is mainly buffered so have a look on the output side of these high speed buffers.

The M3 chips can hold the CPU interrupt low and so freeze the unit and this is where I would look first. 

It turned out that that on  mine, although I can get mine to at least display a M3 interrupt fail on the first test, was a failed M3 chip.


All the best
Royce


--- In vintagesynthrepair@yahoogroups.com, "m.sislack" <m.sislack@...> wrote:
>
> Hi Royce,
> 
> of course i have but even when i try to enter the diagnostic mode it freezes immediately.
> 
> Thanks for your suggestion anyway
> 
> moe
> 
> --- In vintagesynthrepair@yahoogroups.com, "Royce" <rpcfender@> wrote:
> >
> > Hi Moe
> > have you tried the diagnostics?
> > 
> > Press and hold VOICE
> > Press and hold BANK D
> > Press 8
> > 
> > All the best
> > Royce
> > 
> > --- In vintagesynthrepair@yahoogroups.com, "m.sislack" <m.sislack@> wrote:
> > >
> > > Hi Paul, 
> > > 
> > > thanks for your quick reply. The CR2032 has already been changed, all parts, boards, ics and cables i have dis- and then reassembled and reseated, I also replaced all of the electrolytc capacitors on the mainboard, but the problem still persists...
> > > 
> > > regards  moe
> > > 
> > > --- In vintagesynthrepair@yahoogroups.com, Paul Krull <paul.krull@> wrote:
> > > >
> > > > Â You may need to replace the CR2032 batteries and reinitialize the SY77. A cable or chip could be unseated too.
> > > > Â  Â Thanks
> > > > 
> > > > 
> > > > ________________________________
> > > >  From: m.sislack <m.sislack@>
> > > > To: vintagesynthrepair@yahoogroups.com 
> > > > Sent: Sunday, June 9, 2013 8:27 AM
> > > > Subject: [vintagesynthrepair] YAMAHA SY77 freezes
> > > >  
> > > > 
> > > > 
> > > > Â  
> > > > Hello everybody,
> > > > 
> > > > I´m trying to repair an SY77, that when I got it was stuck in untility-mode. It freezes when one of the "mode"-buttons is pressed, so I cannot even enter the test-mode. Furthermore the wheels dont´t have any effect on the sound, but send midi-data. Anyone who experienced an similar problem or could provide any suggestions?
> > > > 
> > > > best regards
> > > > 
> > > > moe
> > > >
> > >
> >
>