Vintage Synth Repair

Well I now fairly certain that it is the M3PCM (YM7115) chip.
I have no desire to try and replace the chip, but I would like to get a new DM2 board (XG525). This is the voice board.

Yes, I can hear you laugh, but perhaps someone knows where there might be one sitting on a shelf.

Perhaps there is another damaged SY77 with a good DM2 board?
Does anyone know if the TG77 used the same board?

Thanks for the help
Royce

>

--- In vintagesynthrepair@yahoogroups.com, "Royce" <rpcfender@...> wrote:
>
> More info...
> When playing the synth the multiples of the 13th and 14th notes fail to sound or sound strange. 
> 
> My first thought would be the SRAM, but the SRAM is tested and passes the first test (TEST A).
> 
> Any ideas?
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, "Royce" <rpcfender@> wrote:
> >
> > Thanks Lorne
> > 
> > 
> > > I'd believe the test and look at the physical circuit at those ICs.  If
> > > socketed I would carefully photograph the circuit, static free pull the ICs
> > > out of any sockets and desolder the sockets and put in new ones.  I would
> > > gently reheat solder connections to resistors and caps immediately around
> > > the ICs and replace any transistor.
> > 
> > The M3s are soldered surface mount. Cleaned the tracks
> > The IRQs seem perfectly good (with a better CRO probe)
> > 
> > >I am thinking cold solder or
> > > microfracture breaks, failed component but usually not any ceramic caps or
> > > resistors.  I never trust old IC sockets.  I would look closely at any logic
> > > ICs as well.  If your clock is okay and shows up at the chip's IN pin then
> > > its not that.  Its iss rare that the wavetable samples are messed up, unless
> > > someone has had a magnet around.  I'd definitely change the decoupling
> > > electrolytics.   Lorne in Canada
> > 
> > Re-soldered the resistors but no luck.
> > 
> > Thanks Lorne
> > > 
> > >  
> > > 
> > > From: vintagesynthrepair@yahoogroups.com
> > > [mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of Royce
> > > Sent: Saturday, February 16, 2013 6:08 AM
> > > To: vintagesynthrepair@yahoogroups.com
> > > Subject: [vintagesynthrepair] Re: Yamaha SY77 faulty
> > > 
> > >  
> > > 
> > >   
> > > 
> > > Any experienced Yamaha techs out there?
> > > 
> > > The story so far...
> > > I have reseated all of the EPROMs and CPU and all the cable connects.
> > > No leaking Li battery so no board corrosion.
> > > 
> > > Looking at the DM2 board the supply is 5V02 with digital ground and 12V1 and
> > > -12V2 with analog ground and a line marked MTAG at 14V going to what looks
> > > like a comparator cct outputting a MUTE signal that turns the audio output
> > > off, probably used at power on and off.
> > > There is a 5V and -5V pair of regs (off the +12 and -12V ) on the analog
> > > board buried underneath that I haven't checked.
> > > 
> > > Only caps on the DM2 board are PS decoupling electros and decoupling
> > > ceramics for the chips and a couple of ceramics for the crystal clock.
> > > 
> > > On the M3 chips there is a CLKMEL and a CLK3 pin.
> > > The CLK3 is grounded and CLKMEL looks like an FX clock.
> > > A CRO on this and it works on and off during boot then goes off until a note
> > > is played. So I guess the clock oscillator for the M3s are working. I've no
> > > idea about timing though.
> > > 
> > > The M3 IRQ is open collector and the pullup resistors all look good.
> > > Like the CLKMEL the IRQ line oscillates in bursts which go on and off during
> > > boot and when a key is pressed post boot there is a constant stream at a
> > > varying frequency.
> > > 
> > > Anyone know what the IRQ error message in the test B means???
> > > 
> > > Thanks for the help. I could be a bit out of my depth here.
> > > 
> > > Any pointers would be gratefully received.
> > > 
> > > All the best
> > > Royce 
> > > 
> > > --- In vintagesynthrepair@yahoogroups.com
> > > <mailto:vintagesynthrepair%40yahoogroups.com> , "Royce" wrote:
> > > >
> > > > The unit arrived with missing screws in the case. 
> > > > Always a bad sign.
> > > > 
> > > > The service manual, kindly given to me (also the one on the web), is only
> > > 71 pages and really only goes through the tests.
> > > > 
> > > > My DX7 and TQ5 service manual are much more detailed.
> > > > Were these synths just 'swap the board" type devices?
> > > > 
> > > > Anyway the test stops at the self test with a message "* M3 IRQ CHECK
> > > ERROR. TEST ABORTED *" and you can't go on to the other tests.
> > > > The service manual only say "If Test B" the M3 test " is NG" no good "then
> > > the error may be related to one of the M3 IC's IRQ levels"
> > > > What does that mean??
> > > > 
> > > > The 2 M3 chips YM7119 are on the DM2 board have something to do with the
> > > Wave ROMs.
> > > > Is this test trying to read all the Wave ROMs and failing?
> > > > Is the CPU just timing out because the M3 isn't returning soon enough?
> > > > It's the interupt request part I don't get.
> > > > 
> > > > Anyone with any more info about this chip?
> > > > Anyone had this problem and managed to get past the IRQ test ?
> > > > 
> > > > I can get a few weird notes out but it sounds like misaddressing of the
> > > Wave ROMs and locks up fairly quickly. 
> > > > 
> > > > Thanks for the help
> > > > Royce
> > > >
> > >
> >
>