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2009-02-23 by Russ
2009-02-24 by selloutdesigns
I gave this a try on my dead Poly, but no luck. It seems that VR1 adjusts the +5V rail voltage and subsequently the supply voltage to the CPU, but in my case it seems like all the chips are getting adequate power. <<aaRoN>> --- In korgpolyex@yahoogroups.com, Russ <russdaren@...> wrote: > > I had this problem a while ago and got her back upby fiddling with one of the VR pots. Cant recal which one did it. But one of them seemed to control voltage for the CPU board. It wnet from no display, to garbled, to functioning just fine ever since. >
2009-02-24 by Michael Hawkins
I gave this a try on my dead Poly, but no luck. It seems that VR1
adjusts the +5V rail voltage and subsequently the supply voltage to
the CPU, but in my case it seems like all the chips are getting
adequate power.
<>
--- In korgpolyex@yahoogro ups.com, Russ wrote:
>
> I had this problem a while ago and got her back upby fiddling with
one of the VR pots. Cant recal which one did it. But one of them
seemed to control voltage for the CPU board. It wnet from no display,
to garbled, to functioning just fine ever since.
>
2009-02-25 by selloutdesigns
Took another look internally last night. There was some sticky gunk on some of the boards which may have been from a battery compartment leak at some point, but it cleaned up fine and there appears to be no trace or component damage. As best I can tell, all the rails are showing correct voltages. Strangely I found that the rails on the main board differed slightly from the smaller board (KLM-598), being about 4.6V. However, adjusting VR1 slightly boosted this voltage to 5V, while causing voltage rails on the main board to be slightly above 5V. I am guessing this is all within tolerable range though. I also took voltage measurements on all the pins on IC24 (M80C85A) and IC25 (M81C55). I see a voltage on all the output pins of IC24 connecting to the input pins of IC25. However, the output pins of IC25 (which feed the display driver circuit) all show 0V. IC24 and 25 both are powered. I did notice that IO/M (both), RESOUT (IC24) and RES (IC25) were showing 0V. Is it correct to assume that if IO/M is always low, that IC25 will never output any data? What would be keeping IC24 from toggling IO/M to high? Thanks in advance for any insight/guidance. Anyone have scans of a Poly 800 Service Manual they can share? :) --- In korgpolyex@yahoogroups.com, Michael Hawkins <korgpolyex800@...> wrote: > > Aaron, > > you should check all voltage rails. especially +5 and -5 volt rails. > > The power supply of the Poly is somewhat reliable. Note the "somewhat". > > Sometimes it does fail or drift enough to cause Poly's to die. > > If you don't have a display showing then tape and patches etc are 99 percent NOT going to work. > > Even when memory is corrupted due to battery failure, those display's will at least show something. > > Also, I would give the thing a complete internal thorough check out looking for battery acid damage, broken wires, misaligned or misplaced connectors etc.
> > Sometimes it's the simple things. > > Mike. > > > > > > ________________________________ > From: selloutdesigns <aah_public@...> > To: korgpolyex@yahoogroups.com > Sent: Tuesday, February 24, 2009 9:48:45 AM > Subject: [korgpolyex] Re: Dead 800 > > > I gave this a try on my dead Poly, but no luck. It seems that VR1 > adjusts the +5V rail voltage and subsequently the supply voltage to > the CPU, but in my case it seems like all the chips are getting > adequate power. > > <<aaRoN>> > --- In korgpolyex@yahoogro ups.com, Russ <russdaren@ ..> wrote: > > > > I had this problem a while ago and got her back upby fiddling with > one of the VR pots. Cant recal which one did it. But one of them > seemed to control voltage for the CPU board. It wnet from no display, > to garbled, to functioning just fine ever since. > > >
2009-02-25 by LARRY HAWKE
2009-02-25 by selloutdesigns
I haven't actually tested the LED displays themselves, but since the display driver chips (IC30 and 31) are not outputting anything to the LED's int he display it seems the issue is there (or probably somewhere earlier in the cycle). I think I am about cave and pick up an oscilloscope for this project (and others!). Any recommendations on a good cheap scope for synth projects to look for used? <<aaRoN>> --- In korgpolyex@yahoogroups.com, LARRY HAWKE <gorgarh@...> wrote: > > > Do you think there's the 'slightest' possibility the display itself might be dead? > > To: korgpolyex@yahoogroups.com > From: aah_public@... > Date: Wed, 25 Feb 2009 15:57:05 +0000 > Subject: [korgpolyex] Re: Dead 800 > > > > > > > > > > > > > > > > > > > > > > Took another look internally last night. There was some sticky gunk on > > some of the boards which may have been from a battery compartment leak > > at some point, but it cleaned up fine and there appears to be no trace > > or component damage. As best I can tell, all the rails are showing > > correct voltages. Strangely I found that the rails on the main board > > differed slightly from the smaller board (KLM-598), being about 4.6V. > > However, adjusting VR1 slightly boosted this voltage to 5V, while > > causing voltage rails on the main board to be slightly above 5V. I am > > guessing this is all within tolerable range though. > > > > I also took voltage measurements on all the pins on IC24 (M80C85A) and > > IC25 (M81C55). I see a voltage on all the output pins of IC24 > > connecting to the input pins of IC25. However, the output pins of IC25 > > (which feed the display driver circuit) all show 0V. IC24 and 25 both > > are powered. I did notice that IO/M (both), RESOUT (IC24) and RES > > (IC25) were showing 0V. Is it correct to assume that if IO/M is always > > low, that IC25 will never output any data? What would be keeping IC24 > > from toggling IO/M to high? > > > > Thanks in advance for any insight/guidance. Anyone have scans of a > > Poly 800 Service Manual they can share? :) > > > > --- In korgpolyex@yahoogroups.com, Michael Hawkins <korgpolyex800@> > > wrote: > > > > > > Aaron, > > > > > > you should check all voltage rails. especially +5 and -5 volt rails. > > > > > > The power supply of the Poly is somewhat reliable. Note the "somewhat".
> > > > > > Sometimes it does fail or drift enough to cause Poly's to die. > > > > > > If you don't have a display showing then tape and patches etc are 99 > > percent NOT going to work. > > > > > > Even when memory is corrupted due to battery failure, those > > display's will at least show something. > > > > > > Also, I would give the thing a complete internal thorough check out > > looking for battery acid damage, broken wires, misaligned or misplaced > > connectors etc. > > > > > > Sometimes it's the simple things. > > > > > > Mike. > > > > > > > > > > > > > > > > > > ________________________________ > > > From: selloutdesigns <aah_public@> > > > To: korgpolyex@yahoogroups.com > > > Sent: Tuesday, February 24, 2009 9:48:45 AM > > > Subject: [korgpolyex] Re: Dead 800 > > > > > > > > > I gave this a try on my dead Poly, but no luck. It seems that VR1 > > > adjusts the +5V rail voltage and subsequently the supply voltage to > > > the CPU, but in my case it seems like all the chips are getting > > > adequate power. > > > > > > <<aaRoN>> > > > --- In korgpolyex@yahoogro ups.com, Russ <russdaren@ ..> wrote: > > > > > > > > I had this problem a while ago and got her back upby fiddling with > > > one of the VR pots. Cant recal which one did it. But one of them > > > seemed to control voltage for the CPU board. It wnet from no display, > > > to garbled, to functioning just fine ever since. > > > > > > > >
2009-02-25 by LARRY HAWKE
2009-02-25 by Gordon JC Pearce
selloutdesigns wrote: > I think I am about cave and pick up an oscilloscope for this project > (and others!). Any recommendations on a good cheap scope for synth > projects to look for used? Any dual-trace scope. One of the good things about oscilloscopes is that you can pick up a perfectly good older scope for very little, which will do everything you need. You don't need digital storage (although it's nice to have). You don't need 100MHz (nice to have). I bought a nice 20MHz dual-trace Iwatsu for \ufffd40 off eBay - I chose that one mostly because the seller was a little south of Glasgow so it was 20 minute's drive to go and pick it up in person (always a good idea with fragile equipment). Don't forget that although it might say "20MHz" on the front, it doesn't just somehow stop working at 20MHz, it just becomes less accurate. I've used my 20MHz scope to align the RF stages of a 70MHz transceiver - since all I wanted to do was see when I had the strongest signal, how accurately it was displayed and how accurate the amplitude measurement was didn't matter at all. The only thing I would say is make sure you get dual-trace. It's quite rare to find modern (<30 years old) scopes that are single-trace, unless they were incredibly cheap or incredibly specialised when they were made. Gordon.
2009-02-25 by Michael Hawkins
Took another look internally last night. There was some sticky gunk on
some of the boards which may have been from a battery compartment leak
at some point, but it cleaned up fine and there appears to be no trace
or component damage. As best I can tell, all the rails are showing
correct voltages. Strangely I found that the rails on the main board
differed slightly from the smaller board (KLM-598), being about 4.6V.
However, adjusting VR1 slightly boosted this voltage to 5V, while
causing voltage rails on the main board to be slightly above 5V. I am
guessing this is all within tolerable range though.
I also took voltage measurements on all the pins on IC24 (M80C85A) and
IC25 (M81C55). I see a voltage on all the output pins of IC24
connecting to the input pins of IC25. However, the output pins of IC25
(which feed the display driver circuit) all show 0V. IC24 and 25 both
are powered. I did notice that IO/M (both), RESOUT (IC24) and RES
(IC25) were showing 0V. Is it correct to assume that if IO/M is always
low, that IC25 will never output any data? What would be keeping IC24
from toggling IO/M to high?
Thanks in advance for any insight/guidance. Anyone have scans of a
Poly 800 Service Manual they can share? :)
--- In korgpolyex@yahoogro ups.com, Michael Hawkins
wrote:
>
> Aaron,
>
> you should check all voltage rails. especially +5 and -5 volt rails.
>
> The power supply of the Poly is somewhat reliable. Note the "somewhat".
>
> Sometimes it does fail or drift enough to cause Poly's to die.
>
> If you don't have a display showing then tape and patches etc are 99
percent NOT going to work.
>
> Even when memory is corrupted due to battery failure, those
display's will at least show something.
>
> Also, I would give the thing a complete internal thorough check out
looking for battery acid damage, broken wires, misaligned or misplaced
connectors etc.
>
> Sometimes it's the simple things.
>
> Mike.
>
>
>
>
>
> ____________ _________ _________ __
> From: selloutdesigns
> To: korgpolyex@yahoogro ups.com
> Sent: Tuesday, February 24, 2009 9:48:45 AM
> Subject: [korgpolyex] Re: Dead 800
>
>
> I gave this a try on my dead Poly, but no luck. It seems that VR1
> adjusts the +5V rail voltage and subsequently the supply voltage to
> the CPU, but in my case it seems like all the chips are getting
> adequate power.
>
> <>
> --- In korgpolyex@yahoogro ups.com, Russ wrote:
> >
> > I had this problem a while ago and got her back upby fiddling with
> one of the VR pots. Cant recal which one did it. But one of them
> seemed to control voltage for the CPU board. It wnet from no display,
> to garbled, to functioning just fine ever since.
> >
>
2009-03-04 by selloutdesigns
I just got my scope and hooked it up last night. The first odd thing I noticed was that CPU RES 7.5 (interrupt oscillator that drives the display and EG/MG among other things) was running at about .34ms per cycle, which is about a 1000 times slower than what it should be (.34usec). Because of the exact 1000x multiplier, I thought maybe I was misreading the scope, but I do not believe I am. For example, when I measure the CPU Clock Out it measures at .3 usec per cycle, but as soon as I switch the probe to CPU RES 7.5 I have to crank up the Time/Div setting. All components check out in that part of the circuit and everything is connected and powered as it should. Any insight as to what might cause this? It does seem if this oscillator is running slow that might be the cause of my display issue. Other oddities which may be related: CPU ALE seems to be slower than normal, at about 1.375usec per cycle vs. .18usec where it is supposed to be. IO/M is always low. On M81C55, Timer Out is always high. Thanks is advance for any guidance anyone may have! <<aaRoN>> --- In korgpolyex@yahoogroups.com, Michael Hawkins <korgpolyex800@...> wrote:
> > If you have goop from what might have been a battery leak then things can look OK but turn out to be alot worse than you think. > > Nevertheless, you might be OK. A scope is going to help alot. > > For example, IO/M signal will spend most of it's time low because it is only high for IO. In the Poly, all of the hardware is mapped into normal memory except for the 81C55. So the IO/M signal is almost 100% low. But a scope will show you thos tiny little 20uS high periods. That would tell you that the CPU was actually doing something as opposed to completely comatose. > > Mike. > > > > > > > ________________________________ > From: selloutdesigns <aah_public@...> > To: korgpolyex@yahoogroups.com > Sent: Wednesday, February 25, 2009 10:57:05 AM > Subject: [korgpolyex] Re: Dead 800 > > > Took another look internally last night. There was some sticky gunk on > some of the boards which may have been from a battery compartment leak > at some point, but it cleaned up fine and there appears to be no trace > or component damage. As best I can tell, all the rails are showing > correct voltages. Strangely I found that the rails on the main board > differed slightly from the smaller board (KLM-598), being about 4.6V. > However, adjusting VR1 slightly boosted this voltage to 5V, while > causing voltage rails on the main board to be slightly above 5V. I am > guessing this is all within tolerable range though. > > I also took voltage measurements on all the pins on IC24 (M80C85A) and > IC25 (M81C55). I see a voltage on all the output pins of IC24 > connecting to the input pins of IC25. However, the output pins of IC25 > (which feed the display driver circuit) all show 0V. IC24 and 25 both > are powered. I did notice that IO/M (both), RESOUT (IC24) and RES > (IC25) were showing 0V. Is it correct to assume that if IO/M is always > low, that IC25 will never output any data? What would be keeping IC24 > from toggling IO/M to high? > > Thanks in advance for any insight/guidance. Anyone have scans of a > Poly 800 Service Manual they can share? :) > > --- In korgpolyex@yahoogro ups.com, Michael Hawkins <korgpolyex800@ ...> > wrote: > > > > Aaron, > > > > you should check all voltage rails. especially +5 and -5 volt rails. > > > > The power supply of the Poly is somewhat reliable. Note the "somewhat". > > > > Sometimes it does fail or drift enough to cause Poly's to die. > > > > If you don't have a display showing then tape and patches etc are 99 > percent NOT going to work. > > > > Even when memory is corrupted due to battery failure, those > display's will at least show something. > > > > Also, I would give the thing a complete internal thorough check out > looking for battery acid damage, broken wires, misaligned or misplaced > connectors etc. > > > > Sometimes it's the simple things. > > > > Mike. > > > > > > > > > > > > ____________ _________ _________ __ > > From: selloutdesigns <aah_public@ ...> > > To: korgpolyex@yahoogro ups.com > > Sent: Tuesday, February 24, 2009 9:48:45 AM > > Subject: [korgpolyex] Re: Dead 800 > > > > > > I gave this a try on my dead Poly, but no luck. It seems that VR1 > > adjusts the +5V rail voltage and subsequently the supply voltage to > > the CPU, but in my case it seems like all the chips are getting > > adequate power. > > > > <<aaRoN>> > > --- In korgpolyex@yahoogro ups.com, Russ <russdaren@ ..> wrote: > > > > > > I had this problem a while ago and got her back upby fiddling with > > one of the VR pots. Cant recal which one did it. But one of them > > seemed to control voltage for the CPU board. It wnet from no display, > > to garbled, to functioning just fine ever since. > > > > > >
2009-03-04 by narfman96
Definitely timing issues with IC36b the interrupt oscillator. Try disconnecting the output at R107 and see if it runs at the correct frequency. If it does the CPU is loading it down somehow. If not then suspect the timing caps C76 or C79. The resistors R102-R104 need to be verified and then the Tl072 op amp itself. This circuit needs to run in the mhz or no go for the LED display and envelope generators. --- In korgpolyex@yahoogroups.com, "selloutdesigns" <aah_public@...> wrote:
> > I just got my scope and hooked it up last night. The first odd thing I noticed was that CPU RES 7.5 (interrupt oscillator that drives the display and EG/MG among other things) was running at about .34ms per cycle, which is about a 1000 times slower than what it should be (.34usec). Because of the exact 1000x multiplier, I thought maybe I was misreading the scope, but I do not believe I am. For example, when I measure the CPU Clock Out it measures at .3 usec per cycle, but as soon as I switch the probe to CPU RES 7.5 I have to crank up the Time/Div setting. All components check out in that part of the circuit and everything is connected and powered as it should. Any insight as to what might cause this? It does seem if this oscillator is running slow that might be the cause of my display issue. > > Other oddities which may be related: CPU ALE seems to be slower than normal, at about 1.375usec per cycle vs. .18usec where it is supposed to be. IO/M is always low. On M81C55, Timer Out is always high. > > Thanks is advance for any guidance anyone may have! > > <<aaRoN>> > > --- In korgpolyex@yahoogroups.com, Michael Hawkins <korgpolyex800@> wrote: > > > > If you have goop from what might have been a battery leak then things can look OK but turn out to be alot worse than you think. > > > > Nevertheless, you might be OK. A scope is going to help alot. > > > > For example, IO/M signal will spend most of it's time low because it is only high for IO. In the Poly, all of the hardware is mapped into normal memory except for the 81C55. So the IO/M signal is almost 100% low. But a scope will show you thos tiny little 20uS high periods. That would tell you that the CPU was actually doing something as opposed to completely comatose. > > > > Mike. > > > > > > > > > > > > > > ________________________________ > > From: selloutdesigns <aah_public@> > > To: korgpolyex@yahoogroups.com > > Sent: Wednesday, February 25, 2009 10:57:05 AM > > Subject: [korgpolyex] Re: Dead 800 > > > > > > Took another look internally last night. There was some sticky gunk on > > some of the boards which may have been from a battery compartment leak > > at some point, but it cleaned up fine and there appears to be no trace > > or component damage. As best I can tell, all the rails are showing > > correct voltages. Strangely I found that the rails on the main board > > differed slightly from the smaller board (KLM-598), being about 4.6V. > > However, adjusting VR1 slightly boosted this voltage to 5V, while > > causing voltage rails on the main board to be slightly above 5V. I am > > guessing this is all within tolerable range though. > > > > I also took voltage measurements on all the pins on IC24 (M80C85A) and > > IC25 (M81C55). I see a voltage on all the output pins of IC24 > > connecting to the input pins of IC25. However, the output pins of IC25 > > (which feed the display driver circuit) all show 0V. IC24 and 25 both > > are powered. I did notice that IO/M (both), RESOUT (IC24) and RES > > (IC25) were showing 0V. Is it correct to assume that if IO/M is always > > low, that IC25 will never output any data? What would be keeping IC24 > > from toggling IO/M to high? > > > > Thanks in advance for any insight/guidance. Anyone have scans of a > > Poly 800 Service Manual they can share? :) > > > > --- In korgpolyex@yahoogro ups.com, Michael Hawkins <korgpolyex800@ ...> > > wrote: > > > > > > Aaron, > > > > > > you should check all voltage rails. especially +5 and -5 volt rails. > > > > > > The power supply of the Poly is somewhat reliable. Note the "somewhat". > > > > > > Sometimes it does fail or drift enough to cause Poly's to die. > > > > > > If you don't have a display showing then tape and patches etc are 99 > > percent NOT going to work. > > > > > > Even when memory is corrupted due to battery failure, those > > display's will at least show something. > > > > > > Also, I would give the thing a complete internal thorough check out > > looking for battery acid damage, broken wires, misaligned or misplaced > > connectors etc. > > > > > > Sometimes it's the simple things. > > > > > > Mike. > > > > > > > > > > > > > > > > > > ____________ _________ _________ __ > > > From: selloutdesigns <aah_public@ ...> > > > To: korgpolyex@yahoogro ups.com > > > Sent: Tuesday, February 24, 2009 9:48:45 AM > > > Subject: [korgpolyex] Re: Dead 800 > > > > > > > > > I gave this a try on my dead Poly, but no luck. It seems that VR1 > > > adjusts the +5V rail voltage and subsequently the supply voltage to > > > the CPU, but in my case it seems like all the chips are getting > > > adequate power. > > > > > > <<aaRoN>> > > > --- In korgpolyex@yahoogro ups.com, Russ <russdaren@ ..> wrote: > > > > > > > > I had this problem a while ago and got her back upby fiddling with > > > one of the VR pots. Cant recal which one did it. But one of them > > > seemed to control voltage for the CPU board. It wnet from no display, > > > to garbled, to functioning just fine ever since. > > > > > > > > > >
2009-03-04 by Gordon JC Pearce MM3YEQ
On Wed, 2009-03-04 at 13:34 +0000, narfman96 wrote: > Definitely timing issues with IC36b the interrupt oscillator. Try > disconnecting the output at R107 and see if it runs at the correct > frequency. If it does the CPU is loading it down somehow. If not then > suspect the timing caps C76 or C79. The resistors R102-R104 need to be > verified and then the Tl072 op amp itself. This circuit needs to run > in the mhz or no go for the LED display and envelope generators. Bah. Just change the TL072 on spec. Horrible things. Gordon
2009-03-04 by selloutdesigns
Anyone know offhand if a tl082 can safely replace a tl072? They do appear compatible. Thanks, <<aaRoN>> --- In korgpolyex@yahoogroups.com, Gordon JC Pearce MM3YEQ <gordon@...> wrote:
> > On Wed, 2009-03-04 at 13:34 +0000, narfman96 wrote: > > Definitely timing issues with IC36b the interrupt oscillator. Try > > disconnecting the output at R107 and see if it runs at the correct > > frequency. If it does the CPU is loading it down somehow. If not then > > suspect the timing caps C76 or C79. The resistors R102-R104 need to be > > verified and then the Tl072 op amp itself. This circuit needs to run > > in the mhz or no go for the LED display and envelope generators. > > Bah. Just change the TL072 on spec. Horrible things. > > Gordon >
2009-03-04 by narfman96
Should work fine. Install a good socket if you want. Then you can use a TL072 when you get one. --- In korgpolyex@yahoogroups.com, "selloutdesigns" <aah_public@...> wrote:
> > Anyone know offhand if a tl082 can safely replace a tl072? They do appear compatible. > > Thanks, > > <<aaRoN>> > > --- In korgpolyex@yahoogroups.com, Gordon JC Pearce MM3YEQ <gordon@> wrote: > > > > On Wed, 2009-03-04 at 13:34 +0000, narfman96 wrote: > > > Definitely timing issues with IC36b the interrupt oscillator. Try > > > disconnecting the output at R107 and see if it runs at the correct > > > frequency. If it does the CPU is loading it down somehow. If not then > > > suspect the timing caps C76 or C79. The resistors R102-R104 need to be > > > verified and then the Tl072 op amp itself. This circuit needs to run > > > in the mhz or no go for the LED display and envelope generators. > > > > Bah. Just change the TL072 on spec. Horrible things. > > > > Gordon > > >
2009-03-04 by selloutdesigns
Hmm, now I am starting to think I'm chasing my tail. In the schematic (pg 6 in Service Manual) for the main board, it shows CPU RES 7.5 as running at .34usec per cycle, or about 2.94 Mhz, which is what got me thinking I had a problem there. However, in the description of the Interrupt Oscillator circuit in the Service Guide (pg 18) it reads: "This oscillator cycle is used for the EG, MG, LED displays, and S/H time division processing. Oscillator frequency is 24OOHz-360OHz. Interrupt order is by priority. If this circuit fails, EG operation and LED indication may become erratic." I measured the oscillator at about .34msec per cycle, or 2941Hz, which seems normal according to that. So which is correct? The schematic or the circuit description? I'm starting to think the circuit description. I've tested all the components except the TL072, but all seem fine. <<aaRoN>> 6) -Address Decoder: --- In korgpolyex@yahoogroups.com, "narfman96" <narfman96@...> wrote:
> > Should work fine. Install a good socket if you want. Then you can use a TL072 when you get one. > > --- In korgpolyex@yahoogroups.com, "selloutdesigns" <aah_public@> wrote: > > > > Anyone know offhand if a tl082 can safely replace a tl072? They do appear compatible. > > > > Thanks, > > > > <<aaRoN>> > > > > --- In korgpolyex@yahoogroups.com, Gordon JC Pearce MM3YEQ <gordon@> wrote: > > > > > > On Wed, 2009-03-04 at 13:34 +0000, narfman96 wrote: > > > > Definitely timing issues with IC36b the interrupt oscillator. Try > > > > disconnecting the output at R107 and see if it runs at the correct > > > > frequency. If it does the CPU is loading it down somehow. If not then > > > > suspect the timing caps C76 or C79. The resistors R102-R104 need to be > > > > verified and then the Tl072 op amp itself. This circuit needs to run > > > > in the mhz or no go for the LED display and envelope generators. > > > > > > Bah. Just change the TL072 on spec. Horrible things. > > > > > > Gordon > > > > > >
2009-03-04 by Michael Hawkins
Hmm, now I am starting to think I'm chasing my tail. In the schematic (pg 6 in Service Manual) for the main board, it shows CPU RES 7.5 as running at .34usec per cycle, or about 2.94 Mhz, which is what got me thinking I had a problem there. However, in the description of the Interrupt Oscillator circuit in the Service Guide (pg 18) it reads:
"This oscillator cycle is used for the EG, MG, LED displays, and S/H time division processing. Oscillator frequency is 24OOHz-360OHz. Interrupt order is by priority. If this circuit fails, EG operation and LED indication may become erratic."
I measured the oscillator at about .34msec per cycle, or 2941Hz, which seems normal according to that.
So which is correct? The schematic or the circuit description? I'm starting to think the circuit description. I've tested all the components except the TL072, but all seem fine.
<>
6) -Address Decoder:
--- In korgpolyex@yahoogro ups.com, "narfman96" wrote:
>
> Should work fine. Install a good socket if you want. Then you can use a TL072 when you get one.
>
> --- In korgpolyex@yahoogro ups.com, "selloutdesigns" wrote:
> >
> > Anyone know offhand if a tl082 can safely replace a tl072? They do appear compatible.
> >
> > Thanks,
> >
> > <>
> >
> > --- In korgpolyex@yahoogro ups.com, Gordon JC Pearce MM3YEQ wrote:
> > >
> > > On Wed, 2009-03-04 at 13:34 +0000, narfman96 wrote:
> > > > Definitely timing issues with IC36b the interrupt oscillator. Try
> > > > disconnecting the output at R107 and see if it runs at the correct
> > > > frequency. If it does the CPU is loading it down somehow. If not then
> > > > suspect the timing caps C76 or C79. The resistors R102-R104 need to be
> > > > verified and then the Tl072 op amp itself. This circuit needs to run
> > > > in the mhz or no go for the LED display and envelope generators.
> > >
> > > Bah. Just change the TL072 on spec. Horrible things.
> > >
> > > Gordon
> > >
> >
>
2009-03-05 by zoinky420
--- In korgpolyex@yahoogroups.com, "selloutdesigns" <aah_public@...> wrote: > > Anyone know offhand if a tl082 can safely replace a tl072? They do appear compatible. > tl072 is the 'low noise' version of tl082, but I wonder if tl062, which is the 'battery power' version would extend Poly800 battery life?? "1mA for the TL072 against less than 500uA for the TL062"
> Thanks, > > <<aaRoN>> > > --- In korgpolyex@yahoogroups.com, Gordon JC Pearce MM3YEQ <gordon@> wrote: > > > > On Wed, 2009-03-04 at 13:34 +0000, narfman96 wrote: > > > Definitely timing issues with IC36b the interrupt oscillator. Try > > > disconnecting the output at R107 and see if it runs at the correct > > > frequency. If it does the CPU is loading it down somehow. If not then > > > suspect the timing caps C76 or C79. The resistors R102-R104 need to be > > > verified and then the Tl072 op amp itself. This circuit needs to run > > > in the mhz or no go for the LED display and envelope generators. > > > > Bah. Just change the TL072 on spec. Horrible things. > > > > Gordon > > >
2009-03-06 by selloutdesigns
Okay, I'm totally stumped at this point. The main issue I see now with the display is that the IO/M pin on the CPU is low 100% of the time, as confirmed with a scope reading. However, I have no idea why. SOD is also low all the time as well, which is probably related. The CPU clock is fine and I see RD,WR,S0,S1 going high and low on a regular basis so it seems memory reads and writes are occurring fine, but no I/O whatsoever. I'm wondering if there is an issue with the CPU receiving instructions from memory, which is causing the I/O cycle to never occur. In any case, I have just about given up in trying to figure out what's going on. I think this unit is destined to land on someone else's bench. If it does get fixed I'll be sure to find out what the cause was. Thanks to all for the input. <<aaRoN>> --- In korgpolyex@yahoogroups.com, Michael Hawkins <korgpolyex800@...> wrote:
> > The circuit description is correct. > > Interrupt RES7.5 runs at around 2400 to 3600 hz. > > It can't run too fast otherwise the CPU won't do anything else except service this hardware interrupt. > > A rate of 2.94Mhz is only half the full clock rate of the CPU. So at that speed, the CPU would not even get to fetch one instruction before being interrupted. > > Mike. > > > > > > ________________________________ > From: selloutdesigns <aah_public@...> > To: korgpolyex@yahoogroups.com > Sent: Wednesday, March 4, 2009 4:22:11 PM > Subject: [korgpolyex] Re: Dead 800 > > > Hmm, now I am starting to think I'm chasing my tail. In the schematic (pg 6 in Service Manual) for the main board, it shows CPU RES 7.5 as running at .34usec per cycle, or about 2.94 Mhz, which is what got me thinking I had a problem there. However, in the description of the Interrupt Oscillator circuit in the Service Guide (pg 18) it reads: > > "This oscillator cycle is used for the EG, MG, LED displays, and S/H time division processing. Oscillator frequency is 24OOHz-360OHz. Interrupt order is by priority. If this circuit fails, EG operation and LED indication may become erratic." > > I measured the oscillator at about .34msec per cycle, or 2941Hz, which seems normal according to that. > > So which is correct? The schematic or the circuit description? I'm starting to think the circuit description. I've tested all the components except the TL072, but all seem fine. > > <<aaRoN>> > > 6) -Address Decoder: > > --- In korgpolyex@yahoogro ups.com, "narfman96" <narfman96@ ..> wrote: > > > > Should work fine. Install a good socket if you want. Then you can use a TL072 when you get one. > > > > --- In korgpolyex@yahoogro ups.com, "selloutdesigns" <aah_public@ > wrote: > > > > > > Anyone know offhand if a tl082 can safely replace a tl072? They do appear compatible. > > > > > > Thanks, > > > > > > <<aaRoN>> > > > > > > --- In korgpolyex@yahoogro ups.com, Gordon JC Pearce MM3YEQ <gordon@> wrote: > > > > > > > > On Wed, 2009-03-04 at 13:34 +0000, narfman96 wrote: > > > > > Definitely timing issues with IC36b the interrupt oscillator. Try > > > > > disconnecting the output at R107 and see if it runs at the correct > > > > > frequency. If it does the CPU is loading it down somehow. If not then > > > > > suspect the timing caps C76 or C79. The resistors R102-R104 need to be > > > > > verified and then the Tl072 op amp itself. This circuit needs to run > > > > > in the mhz or no go for the LED display and envelope generators. > > > > > > > > Bah. Just change the TL072 on spec. Horrible things. > > > > > > > > Gordon > > > > > > > > > >
2009-03-06 by Michael Hawkins
Okay, I'm totally stumped at this point. The main issue I see now with the display is that the IO/M pin on the CPU is low 100% of the time, as confirmed with a scope reading. However, I have no idea why. SOD is also low all the time as well, which is probably related. The CPU clock is fine and I see RD,WR,S0,S1 going high and low on a regular basis so it seems memory reads and writes are occurring fine, but no I/O whatsoever. I'm wondering if there is an issue with the CPU receiving instructions from memory, which is causing the I/O cycle to never occur.
In any case, I have just about given up in trying to figure out what's going on. I think this unit is destined to land on someone else's bench. If it does get fixed I'll be sure to find out what the cause was.
Thanks to all for the input.
<>
--- In korgpolyex@yahoogro ups.com, Michael Hawkins wrote:
>
> The circuit description is correct.
>
> Interrupt RES7.5 runs at around 2400 to 3600 hz.
>
> It can't run too fast otherwise the CPU won't do anything else except service this hardware interrupt.
>
> A rate of 2.94Mhz is only half the full clock rate of the CPU. So at that speed, the CPU would not even get to fetch one instruction before being interrupted.
>
> Mike.
>
>
>
>
>
> ____________ _________ _________ __
> From: selloutdesigns
> To: korgpolyex@yahoogro ups.com
> Sent: Wednesday, March 4, 2009 4:22:11 PM
> Subject: [korgpolyex] Re: Dead 800
>
>
> Hmm, now I am starting to think I'm chasing my tail. In the schematic (pg 6 in Service Manual) for the main board, it shows CPU RES 7.5 as running at .34usec per cycle, or about 2.94 Mhz, which is what got me thinking I had a problem there. However, in the description of the Interrupt Oscillator circuit in the Service Guide (pg 18) it reads:
>
> "This oscillator cycle is used for the EG, MG, LED displays, and S/H time division processing. Oscillator frequency is 24OOHz-360OHz. Interrupt order is by priority. If this circuit fails, EG operation and LED indication may become erratic."
>
> I measured the oscillator at about .34msec per cycle, or 2941Hz, which seems normal according to that.
>
> So which is correct? The schematic or the circuit description? I'm starting to think the circuit description. I've tested all the components except the TL072, but all seem fine.
>
> <>
>
> 6) -Address Decoder:
>
> --- In korgpolyex@yahoogro ups.com, "narfman96" wrote:
> >
> > Should work fine. Install a good socket if you want. Then you can use a TL072 when you get one.
> >
> > --- In korgpolyex@yahoogro ups.com, "selloutdesigns" wrote:
> > >
> > > Anyone know offhand if a tl082 can safely replace a tl072? They do appear compatible.
> > >
> > > Thanks,
> > >
> > > <>
> > >
> > > --- In korgpolyex@yahoogro ups.com, Gordon JC Pearce MM3YEQ wrote:
> > > >
> > > > On Wed, 2009-03-04 at 13:34 +0000, narfman96 wrote:
> > > > > Definitely timing issues with IC36b the interrupt oscillator. Try
> > > > > disconnecting the output at R107 and see if it runs at the correct
> > > > > frequency. If it does the CPU is loading it down somehow. If not then
> > > > > suspect the timing caps C76 or C79. The resistors R102-R104 need to be
> > > > > verified and then the Tl072 op amp itself. This circuit needs to run
> > > > > in the mhz or no go for the LED display and envelope generators.
> > > >
> > > > Bah. Just change the TL072 on spec. Horrible things.
> > > >
> > > > Gordon
> > > >
> > >
> >
>
2009-03-07 by selloutdesigns
I haven't given up on the Poly, just my own ability to get it working in a timely fashion. Possibly if I spent a lot more time I would eventually stumble upon the fix, but fortunately I have a local resource that does vintage synth repair who is taking a look at it now. I'm hoping to have the diagnosis soon, and hopefully a functioning unit. Then I can get back to the important business of modding! <<aaRoN>> --- In korgpolyex@yahoogroups.com, Michael Hawkins <korgpolyex800@...> wrote:
> > Well, you might be giving up a little too early don't you think? > > Remind me again but didn't you say it looked like it had some battery leak on it? > > If that is the case, then I would take a long, hard look at those spots that you think had those leaks on them. > > Because that acid can do it's corrosive thing without showing much damage after you clean it up. > > There is an EPROM in the EPROM socket right? ;-) > > Mike. > > > ________________________________ > From: selloutdesigns <aah_public@...> > To: korgpolyex@yahoogroups.com > Sent: Friday, March 6, 2009 9:53:52 AM > Subject: [korgpolyex] Re: Dead 800 > > > Okay, I'm totally stumped at this point. The main issue I see now with the display is that the IO/M pin on the CPU is low 100% of the time, as confirmed with a scope reading. However, I have no idea why. SOD is also low all the time as well, which is probably related. The CPU clock is fine and I see RD,WR,S0,S1 going high and low on a regular basis so it seems memory reads and writes are occurring fine, but no I/O whatsoever. I'm wondering if there is an issue with the CPU receiving instructions from memory, which is causing the I/O cycle to never occur. > > In any case, I have just about given up in trying to figure out what's going on. I think this unit is destined to land on someone else's bench. If it does get fixed I'll be sure to find out what the cause was. > > Thanks to all for the input. > > <<aaRoN>> > > --- In korgpolyex@yahoogro ups.com, Michael Hawkins <korgpolyex800@ ...> wrote: > > > > The circuit description is correct. > > > > Interrupt RES7.5 runs at around 2400 to 3600 hz. > > > > It can't run too fast otherwise the CPU won't do anything else except service this hardware interrupt. > > > > A rate of 2.94Mhz is only half the full clock rate of the CPU. So at that speed, the CPU would not even get to fetch one instruction before being interrupted. > > > > Mike. > > > > > > > > > > > > ____________ _________ _________ __ > > From: selloutdesigns <aah_public@ ...> > > To: korgpolyex@yahoogro ups.com > > Sent: Wednesday, March 4, 2009 4:22:11 PM > > Subject: [korgpolyex] Re: Dead 800 > > > > > > Hmm, now I am starting to think I'm chasing my tail. In the schematic (pg 6 in Service Manual) for the main board, it shows CPU RES 7.5 as running at .34usec per cycle, or about 2.94 Mhz, which is what got me thinking I had a problem there. However, in the description of the Interrupt Oscillator circuit in the Service Guide (pg 18) it reads: > > > > "This oscillator cycle is used for the EG, MG, LED displays, and S/H time division processing. Oscillator frequency is 24OOHz-360OHz. Interrupt order is by priority. If this circuit fails, EG operation and LED indication may become erratic." > > > > I measured the oscillator at about .34msec per cycle, or 2941Hz, which seems normal according to that. > > > > So which is correct? The schematic or the circuit description? I'm starting to think the circuit description. I've tested all the components except the TL072, but all seem fine. > > > > <<aaRoN>> > > > > 6) -Address Decoder: > > > > --- In korgpolyex@yahoogro ups.com, "narfman96" <narfman96@ ..> wrote: > > > > > > Should work fine. Install a good socket if you want. Then you can use a TL072 when you get one. > > > > > > --- In korgpolyex@yahoogro ups.com, "selloutdesigns" <aah_public@ > wrote: > > > > > > > > Anyone know offhand if a tl082 can safely replace a tl072? They do appear compatible. > > > > > > > > Thanks, > > > > > > > > <<aaRoN>> > > > > > > > > --- In korgpolyex@yahoogro ups.com, Gordon JC Pearce MM3YEQ <gordon@> wrote: > > > > > > > > > > On Wed, 2009-03-04 at 13:34 +0000, narfman96 wrote: > > > > > > Definitely timing issues with IC36b the interrupt oscillator. Try > > > > > > disconnecting the output at R107 and see if it runs at the correct > > > > > > frequency. If it does the CPU is loading it down somehow. If not then > > > > > > suspect the timing caps C76 or C79. The resistors R102-R104 need to be > > > > > > verified and then the Tl072 op amp itself. This circuit needs to run > > > > > > in the mhz or no go for the LED display and envelope generators. > > > > > > > > > > Bah. Just change the TL072 on spec. Horrible things. > > > > > > > > > > Gordon > > > > > > > > > > > > > > >
2009-03-26 by selloutdesigns
So I got my previously dead Poly back last night in fully working order! It turns out the CPU (IC24 80085)had failed somehow and it had shorted and burned out one of the D Flip Flops connected to it (IC 28). Replacing just the flip flop did not work and just immediately burned out the new chip. However, with both of those components replaced everything is back up and running. <<aaRoN>> --- In korgpolyex@yahoogroups.com, "selloutdesigns" <aah_public@...> wrote:
> > I haven't given up on the Poly, just my own ability to get it working in a timely fashion. Possibly if I spent a lot more time I would eventually stumble upon the fix, but fortunately I have a local resource that does vintage synth repair who is taking a look at it now. I'm hoping to have the diagnosis soon, and hopefully a functioning unit. Then I can get back to the important business of modding! > > <<aaRoN>> > > --- In korgpolyex@yahoogroups.com, Michael Hawkins <korgpolyex800@> wrote: > > > > Well, you might be giving up a little too early don't you think? > > > > Remind me again but didn't you say it looked like it had some battery leak on it? > > > > If that is the case, then I would take a long, hard look at those spots that you think had those leaks on them. > > > > Because that acid can do it's corrosive thing without showing much damage after you clean it up. > > > > There is an EPROM in the EPROM socket right? ;-) > > > > Mike. > > > > > > ________________________________ > > From: selloutdesigns <aah_public@> > > To: korgpolyex@yahoogroups.com > > Sent: Friday, March 6, 2009 9:53:52 AM > > Subject: [korgpolyex] Re: Dead 800 > > > > > > Okay, I'm totally stumped at this point. The main issue I see now with the display is that the IO/M pin on the CPU is low 100% of the time, as confirmed with a scope reading. However, I have no idea why. SOD is also low all the time as well, which is probably related. The CPU clock is fine and I see RD,WR,S0,S1 going high and low on a regular basis so it seems memory reads and writes are occurring fine, but no I/O whatsoever. I'm wondering if there is an issue with the CPU receiving instructions from memory, which is causing the I/O cycle to never occur. > > > > In any case, I have just about given up in trying to figure out what's going on. I think this unit is destined to land on someone else's bench. If it does get fixed I'll be sure to find out what the cause was. > > > > Thanks to all for the input. > > > > <<aaRoN>> > > > > --- In korgpolyex@yahoogro ups.com, Michael Hawkins <korgpolyex800@ ...> wrote: > > > > > > The circuit description is correct. > > > > > > Interrupt RES7.5 runs at around 2400 to 3600 hz. > > > > > > It can't run too fast otherwise the CPU won't do anything else except service this hardware interrupt. > > > > > > A rate of 2.94Mhz is only half the full clock rate of the CPU. So at that speed, the CPU would not even get to fetch one instruction before being interrupted. > > > > > > Mike. > > > > > > > > > > > > > > > > > > ____________ _________ _________ __ > > > From: selloutdesigns <aah_public@ ...> > > > To: korgpolyex@yahoogro ups.com > > > Sent: Wednesday, March 4, 2009 4:22:11 PM > > > Subject: [korgpolyex] Re: Dead 800 > > > > > > > > > Hmm, now I am starting to think I'm chasing my tail. In the schematic (pg 6 in Service Manual) for the main board, it shows CPU RES 7.5 as running at .34usec per cycle, or about 2.94 Mhz, which is what got me thinking I had a problem there. However, in the description of the Interrupt Oscillator circuit in the Service Guide (pg 18) it reads: > > > > > > "This oscillator cycle is used for the EG, MG, LED displays, and S/H time division processing. Oscillator frequency is 24OOHz-360OHz. Interrupt order is by priority. If this circuit fails, EG operation and LED indication may become erratic." > > > > > > I measured the oscillator at about .34msec per cycle, or 2941Hz, which seems normal according to that. > > > > > > So which is correct? The schematic or the circuit description? I'm starting to think the circuit description. I've tested all the components except the TL072, but all seem fine. > > > > > > <<aaRoN>> > > > > > > 6) -Address Decoder: > > > > > > --- In korgpolyex@yahoogro ups.com, "narfman96" <narfman96@ ..> wrote: > > > > > > > > Should work fine. Install a good socket if you want. Then you can use a TL072 when you get one. > > > > > > > > --- In korgpolyex@yahoogro ups.com, "selloutdesigns" <aah_public@ > wrote: > > > > > > > > > > Anyone know offhand if a tl082 can safely replace a tl072? They do appear compatible. > > > > > > > > > > Thanks, > > > > > > > > > > <<aaRoN>> > > > > > > > > > > --- In korgpolyex@yahoogro ups.com, Gordon JC Pearce MM3YEQ <gordon@> wrote: > > > > > > > > > > > > On Wed, 2009-03-04 at 13:34 +0000, narfman96 wrote: > > > > > > > Definitely timing issues with IC36b the interrupt oscillator. Try > > > > > > > disconnecting the output at R107 and see if it runs at the correct > > > > > > > frequency. If it does the CPU is loading it down somehow. If not then > > > > > > > suspect the timing caps C76 or C79. The resistors R102-R104 need to be > > > > > > > verified and then the Tl072 op amp itself. This circuit needs to run > > > > > > > in the mhz or no go for the LED display and envelope generators. > > > > > > > > > > > > Bah. Just change the TL072 on spec. Horrible things. > > > > > > > > > > > > Gordon > > > > > > > > > > > > > > > > > > > > >