Vintage Synth Repair

 From: m.sislack <m.sislack@...>
To: vintagesynthrepair@yahoogroups.com 
Sent: Sunday, June 9, 2013 8:27 AM
Subject: [vintagesynthrepair] YAMAHA SY77 freezes
 


  
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

>
> 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
>

>
> 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
> >
>

>
> 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
> > >
> >
>

>
> check your bridge rectifiers in the power supply...if these get to hot the
> synth can freeze. Had a similar problem with a dx7 and a dj set. Swapped
> the BR for ones with higher values and the problem disappearred.
> 
> 
> 2013/6/10 Royce <rpcfender@...>
> 
> > **
> >
> >
> > 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
> > > >
> > >
> >
> >  
> >
>

>
> 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
> > > >
> > >
> >
>

>
> 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
> > > > >
> > > >
> > >
> >
>

> thanks a lot and best regards
> 
> moe
> 
> --- In vintagesynthrepair@yahoogroups.com, "Royce" <rpcfender@> wrote:
> >
> > 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
> > > > > >
> > > > >
> > > >
> > >
> >
>

>
> Hi moe
> 
> > removed the DM2-board and - as you predicted - the SY77 can be used as midi-controller. But even while the DM2-board is removed it freezes when one of the "MODE" is pressed. So I assume that the malfunction is caused by somewhere on the DM1-board, right?
> 
> Maybe. Both the switches/leds, foot switches and the keyboard are scanned and controlled by a separate micro-controller (IC137 on the circuit diagram). 
> Do you have the cct diag?
> If there was a problem there is is likely that it would appear in more that one switch.
> Do you see the failure in different switches or in a complete block?
> 
> Freezing is usually caused by the CPU going into a loop, either software or hardware.
> 
> The hardware freeze can be caused by the 2 interrupt requests(IRQ), the nonmaskable interrupt(NMI), the reset(RES) or the Standby(STBY) pin's state being held.
> IC101, the CPU, has a NMI and STDY that are never used .
> The RES is only controlled when the unit powers up.
> Both the INTs are attached to the M3 chips on the DM2 board.
> 
> So my guess is when you press the Mode buttons the CPU makes a request to the M3 chips (no longer connected) and waits in a software loop for the reply.
> 
> So from this long winded reply I would guess that the DM1 board could still be OK. (I would have to pull my SY77 apart to be sure)
> 
> > Could you tell me which parts are the high-speed-buffers you mentioned and how to test them?
> 
> The buffers are on the DM2 board so you will need to reconnect it.
> IC201 is the 'control' buffer and has the chip selects(CS), marked as FMSEL, M3PCM and M3FM  on it.
> IC203 is the CPU data buffer
> IC202 is the CPU data addressing buffer.
> 
> These are very fast buffers and you will need a good oscilloscope to read them without loading the pins.
> 
> The IRQs are unbuffered so put a oscilloscope on it and make sure you can see a pulse to ground. If it is held to ground then the CPU will be hardware frozen.
> 
> Of course the easiest way is to persuade a friend to let you try out your DM2 card in their SY77 (could be the same board in a TG77 ??) and then put his DM2 board in your synth to start to pin point the problem.
> 
> I tried to find a spare DM2 board from Yamaha, but I ended up buying another part broken SY77 and swapping parts around to make one good synth.
> 
> So if you find a source of DM2 boards let me know so I can get this other one going.
> 
> I am in Melbourne Australia. If you are close, feel free to email me.
> 
> Best of luck
> Royce
>  
> > thanks a lot and best regards
> > 
> > moe
> > 
> > --- In vintagesynthrepair@yahoogroups.com, "Royce" <rpcfender@> wrote:
> > >
> > > 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
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

>
> Hi moe
> 
> > another detail i may not have mentioned yet is that when powering up the sequencer leds flicker for a shorter or longer period of time. And only during this time slot it is possible to execute an "init ram$" which is part of the hidden functions. Could this be a further hint leading to the cause of the malfunction?
> 
> The SY77 has 3 CPUs. A central one for the display, the wheels and rotary encoder and co-coordinating the two others as well as the M3 chips on the DM2 board.
> The second is the switch, led and keyboard one, mentioned before.
> The third is the sequencer CPU which controls the flashing Run LEDs as well as the Record LED and well as doing the record to memory and the playback. It is like a separate  sequencer, but needs to chat to the main CPU.
> 
> I suspect the led flicker is just part of the boot routine for the sequencer CPU (IC145). 
> 
> Because neither of the other two CPUs is connected to an INT line of the central CPU they must be polled.
> So if the switch CPU freezes you couldn't play the keyboard and the switches wouldn't work, but the Midi in should still function.
> Is this is what is happening?
> 
> I did miss an input that might cause freezing on the CPU. There is a WAIT signal line which I am assuming is for the timing for access to the memory and perhaps the other CPUs. So only the M3 chips are time critical and are therefore connected to the INT lines of the CPU.
> 
> I'm not sure what your level of electronics is so forgive me if I suggest the obvious.
> I would start with the following.
> 
> Measure the power supply and the each board's voltages with a digital multimeter (DMM). Note that there is and analog and a separate digital ground. Measure using the correct ground. Check the power pins on EACH of the boards.
> 
> If you don't have an oscilloscope you should check continuity of the connecting cables between the boards with your DMM. I would start at the switch board connectors. Remember to have the power off (perhaps unplugged, as I zapped myself fixing mine). The mode switches you are having trouble with are connected to the main switch board and then to the DM1 board so you have to check two sets of cables.
> 
> If you do have an oscilloscope look at the central CPU (IC101) pins that cause freezing, pin 7 WAIT, 8 & 9 INT (not sure if pin9 is connected but it should be pulled high) and see if any of them are held low.
> 
> Like the keyboard, the switches are read in blocks. In a group one side of the switches are connected together and the CPU polls them as a block and the other sides are read as data lines. Check the switch board to make sure the switch bank lines are being scanned. If they are the Switch CPU is doing something and it is likely you need to look elsewhere. 
> 
> Royce
>