Korg Mono/Poly

Hello.

Just a few moments ago I was playing some music and all of a sudden my mono/poly stopped working. I tried to flip the switch and nothing happens; no lights or sound. (I didn't see or smell smoke)

I opened it up and the fuses are all fine, but the transformer was so hot that I couldn't keep my finger on it for more than a moment (even now, 15 minutes later it is still very warm).
I used the service manual and checked on board 356 for voltages and none of them registered(5, 15, or -15).

I'm not sure what to do now. I'm guessing the transformer died, but how can I know for sure? What would cause the transformer to just go out like that? If it is the transformer, does anyone here have a spare or know where to find one?

Thanks,
Chase

Damn it, nevermind.  One of the fuses is blown.  I don't have a spare right now to replace it so I can't see for sure if it is okay, but I feel more relaxed now. 

So even if I replace this fuse and it seems perfectly fine, wouldn't a fuse blowing be indicative of a problem?  There wasn't really a power surge as far as I could tell and I think this fuse is only a few years old.

Thanks,
Chase

--- On Thu, 11/26/09, plus_321 <plus_321@yahoo.com> wrote:

From: plus_321 <plus_321@yahoo.com>
Subject: [korg_mono-poly] Mono/Poly doesn't turn on. (Transformer gets really hot)
To: korg_mono-poly@yahoogroups.com
Date: Thursday, November 26, 2009, 9:31 PM

Hello.

Just a few moments ago I was playing some music and all of a sudden my mono/poly stopped working.  I tried to flip the switch and nothing happens; no lights or sound.  (I didn't see or smell smoke)

I opened it up and the fuses are all fine, but the transformer was so hot that I couldn't keep my finger on it for more than a moment (even now, 15 minutes later it is still very warm). 
I used the service manual and checked on board 356 for voltages and none of them registered(5, 15, or -15). 

I'm not sure what to do now.  I'm guessing the transformer died, but how can I know for sure?  What would cause the transformer to just go out like that?  If it is the transformer, does anyone here have a spare or know where to find one?

Thanks,
Chase



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Hello Chase

first my usual disclaimer:
THIS MAIL DESCRIBS AN ACTION THAT REQUIRES TO OPEN THE CASE OF THE
MONOPOLY. THIS SHOULD ONLY BE DONE BY PEOPLE, WHO KNOW HOW TO HANDLE THE
DANGEROUS VOLTAGES INSIDE OF THE SYNTH PROPERLY WITHOUT ENDANGERING THE
LIFE OF OTHERS OR THEMSELVES!!! IF YOU DON'T HAVE THE REQUIRED
EXPERIENCE - KEEP YOUR HANDS OFF!!! DOING THE WRONG THINGS INSIDE AN
ELECTRICAL INSTRUMENT MAY KILL YOU OR PEOPLE, THAT RELY ON YOUR WORK. I
WARNED YOU. I REJECT ALL LIABILITY FOR ALL CONSEQUENCES OF THE FOLLOWING
INSTRUCTIONS!

> So even if I replace this fuse and it seems perfectly fine, wouldn't a
> fuse blowing be indicative of a problem? There wasn't really a power
> surge as far as I could tell and I think this fuse is only a few years old.

It might(!) be indicative for a problem - especially because the
transformer was that hot.

I recommend the following procedure:
* Switch of the synth, and remove the powercable from the power outlet
in the wall.
* open up the synth
* take a thick and stabile sheet of paper and cover all parts at the
bottom and rear side of the synth right side of the transformer with it
(powerswitch, main fuse pcb, transformer-connections)
* Do NOT switch on the synth until you replaced the fuse.
* Remove both fuses on the powersupply pcb - still do not switch on the
synth.
* Disconnect all cables from the powersupply pcb with exception of the
cable coming from the transformer.
* Prepare a digital voltmeter, which can read DC and AC up to 50 volts.
* Connect the minus measuring cable to the wire coming out of the right
side of C14 (the largest capacitor on the right side of the power supply
pcb)
* Set the voltmeter to AC
* Plug in the power cable to the power outlet in the wall
* Switch the synth on
* Measure the voltage at the frontside contact of the fuse sockets => it
should read about 15 to 20 Volts, but both contacts should read the same
voltage
* Switch of the synth
* Insert good fuses to the sockets
* Set the voltmeter to DC and be prepared to measure immediately after
switching on the synth
* Switch on the synth
* Measure the voltage at the most rear contacts of diodes D2/D3 and
D4/D5. It should read somthing around 20 to 25 Volts DC; again I can not
tell now exactly what voltage, but it should be the same on both
measuring points.

If any of these measurements fails or if the fuse blows again, then get
the synth to a technician, who knows to handle this.

If the mesaurements before read ok, then:
* Measure the voltages at CN33. They should read from left to right:
+15V, -15V, +5V, 0V. The pins for -15 and +15 may read a little bit
different values like 14.98 or 15.02, but it should NOT be like -15.01
and 17.5; if this is the case, then switch off the synth and bring it to
a tech.
If both read a similar but wrong value like +13 and -13, then try to
adjust the voltage with the trim potentiometer VR3. VR3 affects both
voltages.
If +5V reads a slightly other value (like +5.02) it is ok. If it reads a
very different value (like 9.02), then switch off the synth and bring it
to a tech.


Florian

Chase,
If it turns out that you have a transformer down, I have one that came out of my MonoPoly. I'm in the UK and my MP was for the US market so I changed the transformer for one with a 240V UK primary winding. The one I pulled out is marked with the following so you can check against yours:
BANDO
TA-006
BDI4B2-003A
Those three markings are on the left hand side and:
61-7981
100V
41.0V 37.0VA
These markings are on the right hand side.

Steve

--- In korg_mono-poly@yahoogroups.com, "plus_321" <plus_321@...> wrote:
>
> Hello.
>
> Just a few moments ago I was playing some music and all of a sudden my mono/poly stopped working. I tried to flip the switch and nothing happens; no lights or sound. (I didn't see or smell smoke)
>
> I opened it up and the fuses are all fine, but the transformer was so hot that I couldn't keep my finger on it for more than a moment (even now, 15 minutes later it is still very warm).
> I used the service manual and checked on board 356 for voltages and none of them registered(5, 15, or -15).
>
> I'm not sure what to do now. I'm guessing the transformer died, but how can I know for sure? What would cause the transformer to just go out like that? If it is the transformer, does anyone here have a spare or know where to find one?
>
> Thanks,
> Chase
>

Okay, I did the tests that you suggested and I think they came out okay. I didn't get the exact voltage range that you specified.

I got 25.37 VAC on the fuses and 33.78 VDC on the diodes, but the measurements were consistent so I think it's fine.

I replaced the blown fuse and it's been running fine for a few hours now. Still, I can't help but wonder why the fuse went out.

I have another issue that's bothering me that, I believe, has been around since I got this mono/poly. It has a constant noise coming through the outputs that almost sounds like data noise. I can't seem to upload things now or I would put up a sample.

A while ago, I found through experiementing that if I remove connector CN23 from board 356, then the noise will go away. I remember figuring out that this went to the arpeggiator. I also tested the connector pin to pin from the cable and discovered that the second pin from the left is what creates the noise when connected. I looked through the service manual and found that this pin is for 2OCT arp mode. I pulled it out of the connector, but the arp won't run without it.

A while ago I remember thinking that it was the 8049c since the arp deals with that so I ordered a replacement. Well I just tried to swap the chips and the issue remains so it isn't that. I really need the arp on this guy, because that is part of what makes it unique, but it is hard to deal with noise anymore.. Does this sound like maybe something you've seen or any suggestions on where to look?

I replaced nearly all electrolytic capacitors, voltage regulators, and op amps in this machine so I don't really have any idea what it could be. However, I will not go to a tech. I took this very machine to a tech to fix this problem and the result of that was 3 months away from my keyboard and 200 dollars from my bank account. I can not afford such extravagant fees.

I will appreciate any suggestions. Otherwise, thank you for your time.

Chase

--- In korg_mono-poly@yahoogroups.com, Florian Anwander <fanwander@...> wrote:
>
> Hello Chase
>
> first my usual disclaimer:
> THIS MAIL DESCRIBS AN ACTION THAT REQUIRES TO OPEN THE CASE OF THE
> MONOPOLY. THIS SHOULD ONLY BE DONE BY PEOPLE, WHO KNOW HOW TO HANDLE THE
> DANGEROUS VOLTAGES INSIDE OF THE SYNTH PROPERLY WITHOUT ENDANGERING THE
> LIFE OF OTHERS OR THEMSELVES!!! IF YOU DON'T HAVE THE REQUIRED
> EXPERIENCE - KEEP YOUR HANDS OFF!!! DOING THE WRONG THINGS INSIDE AN
> ELECTRICAL INSTRUMENT MAY KILL YOU OR PEOPLE, THAT RELY ON YOUR WORK. I
> WARNED YOU. I REJECT ALL LIABILITY FOR ALL CONSEQUENCES OF THE FOLLOWING
> INSTRUCTIONS!
>
> > So even if I replace this fuse and it seems perfectly fine, wouldn't a
> > fuse blowing be indicative of a problem? There wasn't really a power
> > surge as far as I could tell and I think this fuse is only a few years old.
> It might(!) be indicative for a problem - especially because the
> transformer was that hot.
>
> I recommend the following procedure:
> * Switch of the synth, and remove the powercable from the power outlet
> in the wall.
> * open up the synth
> * take a thick and stabile sheet of paper and cover all parts at the
> bottom and rear side of the synth right side of the transformer with it
> (powerswitch, main fuse pcb, transformer-connections)
> * Do NOT switch on the synth until you replaced the fuse.
> * Remove both fuses on the powersupply pcb - still do not switch on the
> synth.
> * Disconnect all cables from the powersupply pcb with exception of the
> cable coming from the transformer.
> * Prepare a digital voltmeter, which can read DC and AC up to 50 volts.
> * Connect the minus measuring cable to the wire coming out of the right
> side of C14 (the largest capacitor on the right side of the power supply
> pcb)
> * Set the voltmeter to AC
> * Plug in the power cable to the power outlet in the wall
> * Switch the synth on
> * Measure the voltage at the frontside contact of the fuse sockets => it
> should read about 15 to 20 Volts, but both contacts should read the same
> voltage
> * Switch of the synth
> * Insert good fuses to the sockets
> * Set the voltmeter to DC and be prepared to measure immediately after
> switching on the synth
> * Switch on the synth
> * Measure the voltage at the most rear contacts of diodes D2/D3 and
> D4/D5. It should read somthing around 20 to 25 Volts DC; again I can not
> tell now exactly what voltage, but it should be the same on both
> measuring points.
>
> If any of these measurements fails or if the fuse blows again, then get
> the synth to a technician, who knows to handle this.
>
> If the mesaurements before read ok, then:
> * Measure the voltages at CN33. They should read from left to right:
> +15V, -15V, +5V, 0V. The pins for -15 and +15 may read a little bit
> different values like 14.98 or 15.02, but it should NOT be like -15.01
> and 17.5; if this is the case, then switch off the synth and bring it to
> a tech.
> If both read a similar but wrong value like +13 and -13, then try to
> adjust the voltage with the trim potentiometer VR3. VR3 affects both
> voltages.
> If +5V reads a slightly other value (like +5.02) it is ok. If it reads a
> very different value (like 9.02), then switch off the synth and bring it
> to a tech.
>
>
> Florian
>

Hi Chase

if there is digital noise in the audio, then the problem is typically
wrong or missing grounding.

You may check the power rails with an oscilloscope, whether the digital
noise signal is on the powerrails.
If not: I would use an audio probe (like a multimeter probe, but
connected to an audio amp; ground connected separately) and go through
the complete signal path starting from the VCOs until the output socket.
This should allow to narrow down the cause.

Florian


BTW: Swaping the 8049 doesn't help anything - and also it would have to
be a 8049 for a monopoly. This is a CPU, with embeded PROM. The PROM
content is written once at the factory; a 8049 from a Roland SH-101 is
something completely different from the one in the Korg MonoPoly. So you
need a chip which was produced especially for the related synth.



plus_321 wrote:

> Okay, I did the tests that you suggested and I think they came out okay. I didn't get the exact voltage range that you specified.
>
> I got 25.37 VAC on the fuses and 33.78 VDC on the diodes, but the measurements were consistent so I think it's fine.
>
> I replaced the blown fuse and it's been running fine for a few hours now. Still, I can't help but wonder why the fuse went out.
>
> I have another issue that's bothering me that, I believe, has been around since I got this mono/poly. It has a constant noise coming through the outputs that almost sounds like data noise. I can't seem to upload things now or I would put up a sample.
>
> A while ago, I found through experiementing that if I remove connector CN23 from board 356, then the noise will go away. I remember figuring out that this went to the arpeggiator. I also tested the connector pin to pin from the cable and discovered that the second pin from the left is what creates the noise when connected. I looked through the service manual and found that this pin is for 2OCT arp mode. I pulled it out of the connector, but the arp won't run without it.
>
> A while ago I remember thinking that it was the 8049c since the arp deals with that so I ordered a replacement. Well I just tried to swap the chips and the issue remains so it isn't that. I really need the arp on this guy, because that is part of what makes it unique, but it is hard to deal with noise anymore.. Does this sound like maybe something you've seen or any suggestions on where to look?
>
> I replaced nearly all electrolytic capacitors, voltage regulators, and op amps in this machine so I don't really have any idea what it could be. However, I will not go to a tech. I took this very machine to a tech to fix this problem and the result of that was 3 months away from my keyboard and 200 dollars from my bank account. I can not afford such extravagant fees.
>
> I will appreciate any suggestions. Otherwise, thank you for your time.
>
> Chase
>
> --- In korg_mono-poly@yahoogroups.com, Florian Anwander <fanwander@...> wrote:
>
>>Hello Chase
>>
>>first my usual disclaimer:
>>THIS MAIL DESCRIBS AN ACTION THAT REQUIRES TO OPEN THE CASE OF THE
>>MONOPOLY. THIS SHOULD ONLY BE DONE BY PEOPLE, WHO KNOW HOW TO HANDLE THE
>>DANGEROUS VOLTAGES INSIDE OF THE SYNTH PROPERLY WITHOUT ENDANGERING THE
>>LIFE OF OTHERS OR THEMSELVES!!! IF YOU DON'T HAVE THE REQUIRED
>>EXPERIENCE - KEEP YOUR HANDS OFF!!! DOING THE WRONG THINGS INSIDE AN
>>ELECTRICAL INSTRUMENT MAY KILL YOU OR PEOPLE, THAT RELY ON YOUR WORK. I
>>WARNED YOU. I REJECT ALL LIABILITY FOR ALL CONSEQUENCES OF THE FOLLOWING
>>INSTRUCTIONS!
>>
>>
>>>So even if I replace this fuse and it seems perfectly fine, wouldn't a
>>>fuse blowing be indicative of a problem? There wasn't really a power
>>>surge as far as I could tell and I think this fuse is only a few years old.
>>
>>It might(!) be indicative for a problem - especially because the
>>transformer was that hot.
>>
>>I recommend the following procedure:
>>* Switch of the synth, and remove the powercable from the power outlet
>>in the wall.
>>* open up the synth
>>* take a thick and stabile sheet of paper and cover all parts at the
>>bottom and rear side of the synth right side of the transformer with it
>>(powerswitch, main fuse pcb, transformer-connections)
>>* Do NOT switch on the synth until you replaced the fuse.
>>* Remove both fuses on the powersupply pcb - still do not switch on the
>>synth.
>>* Disconnect all cables from the powersupply pcb with exception of the
>>cable coming from the transformer.
>>* Prepare a digital voltmeter, which can read DC and AC up to 50 volts.
>>* Connect the minus measuring cable to the wire coming out of the right
>>side of C14 (the largest capacitor on the right side of the power supply
>>pcb)
>>* Set the voltmeter to AC
>>* Plug in the power cable to the power outlet in the wall
>>* Switch the synth on
>>* Measure the voltage at the frontside contact of the fuse sockets => it
>>should read about 15 to 20 Volts, but both contacts should read the same
>>voltage
>>* Switch of the synth
>>* Insert good fuses to the sockets
>>* Set the voltmeter to DC and be prepared to measure immediately after
>>switching on the synth
>>* Switch on the synth
>>* Measure the voltage at the most rear contacts of diodes D2/D3 and
>>D4/D5. It should read somthing around 20 to 25 Volts DC; again I can not
>>tell now exactly what voltage, but it should be the same on both
>>measuring points.
>>
>>If any of these measurements fails or if the fuse blows again, then get
>>the synth to a technician, who knows to handle this.
>>
>>If the mesaurements before read ok, then:
>>* Measure the voltages at CN33. They should read from left to right:
>>+15V, -15V, +5V, 0V. The pins for -15 and +15 may read a little bit
>>different values like 14.98 or 15.02, but it should NOT be like -15.01
>>and 17.5; if this is the case, then switch off the synth and bring it to
>>a tech.
>>If both read a similar but wrong value like +13 and -13, then try to
>>adjust the voltage with the trim potentiometer VR3. VR3 affects both
>>voltages.
>>If +5V reads a slightly other value (like +5.02) it is ok. If it reads a
>>very different value (like 9.02), then switch off the synth and bring it
>>to a tech.
>>
>>
>>Florian
>>
>
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>

I tried to use an oscilloscope today to check the power rails. I check them on the 356 board, but the seemed fine and I could see any significant fluctuations.

I realize that when I unplug the VCA out connector or power input on the VCF board then the noise becomes much louder. So I was able to put the scope on the output and see what it looks like. It appears to be a constant frequency pulse wave with a small cycle length, like 5-10%. The noise doesn't go through the filter so it isn't oscillator bleed and it doesn't track the keyboard. The only thing that really affects it is moving the arp switches.

I've found the noise goes away completely if I unplug the arp connector from the 356 board, but if I unplug the same cable from the other end, the noise remains, but is reduced in volume. I checked the cable and it seems good.

So I am thinking that either there is something wrong with my 356 board that is causing this noise or perhaps their is an issue with the cable routing (perhaps maybe it shouldn't be bundled with a power cable or something).

Thanks,
Chase

It could maybe be a Op Amp on that is leaking some timer data in to the signel path.  Haven't get scimatics or anything in front of me now but could be worth checking the outputs on any Op Amp assoctiated with the Arp.

--- On Wed, 2/12/09, plus_321 <plus_321@yahoo.com> wrote:

From: plus_321 <plus_321@yahoo.com>
Subject: [korg_mono-poly] Re: Mono/Poly doesn't turn on. (Transformer gets really hot)
To: korg_mono-poly@yahoogroups.com
Date: Wednesday, 2 December, 2009, 8:23

 

I tried to use an oscilloscope today to check the power rails. I check them on the 356 board, but the seemed fine and I could see any significant fluctuations.

I realize that when I unplug the VCA out connector or power input on the VCF board then the noise becomes much louder. So I was able to put the scope on the output and see what it looks like. It appears to be a constant frequency pulse wave with a small cycle length, like 5-10%. The noise doesn't go through the filter so it isn't oscillator bleed and it doesn't track the keyboard. The only thing that really affects it is moving the arp switches.

I've found the noise goes away completely if I unplug the arp connector from the 356 board, but if I unplug the same cable from the other end, the noise remains, but is reduced in volume. I checked the cable and it seems good.

So I am thinking that either there is something wrong with my 356 board that is causing this noise or perhaps their is an issue with the cable routing (perhaps maybe it shouldn't be bundled with a power cable or something).

Thanks,
Chase

Alan Dicker schrieb:

>
>
> It could maybe be a Op Amp on that is leaking some timer data in to the
> signel path. Haven't get scimatics or anything in front of me now

http://fa.utfs.org/diy/korg_monopoly/index.html

> but could be worth checking the outputs on any Op Amp assoctiated with the Arp.

There are two connections from/to the arpeggiator (which is +5V
circuitry) to the OpAmp-World (which is +/-15V circuitry): The
arpeggiator resets the MG1.
MG1 feeds the Arpeggio Trigger in and the Arpeggio-Switche reset the MG1.
Since the signal at the osci is described like an cyclic enabled adress
line, I think the second option should be the suspected one. It might be
worth to interrupt this connection. It is the wire from LFO-Board
connector 6 pin 10 to uP-board connector 23 pin 10.

Btw: this is a modification I'd recommend anyway, if you do not want to
reset the arp-Clock with every new chord, that you play.

Florian

>
> --- On *Wed, 2/12/09, plus_321 /<plus_321@yahoo.com>/* wrote:
>
>
> From: plus_321 <plus_321@yahoo.com>
> Subject: [korg_mono-poly] Re: Mono/Poly doesn't turn on.
> (Transformer gets really hot)
> To: korg_mono-poly@yahoogroups.com
> Date: Wednesday, 2 December, 2009, 8:23
>
>
>
>
> I tried to use an oscilloscope today to check the power rails. I
> check them on the 356 board, but the seemed fine and I could see any
> significant fluctuations.
>
> I realize that when I unplug the VCA out connector or power input on
> the VCF board then the noise becomes much louder. So I was able to
> put the scope on the output and see what it looks like. It appears
> to be a constant frequency pulse wave with a small cycle length,
> like 5-10%. The noise doesn't go through the filter so it isn't
> oscillator bleed and it doesn't track the keyboard. The only thing
> that really affects it is moving the arp switches.
>
> I've found the noise goes away completely if I unplug the arp
> connector from the 356 board, but if I unplug the same cable from
> the other end, the noise remains, but is reduced in volume. I
> checked the cable and it seems good.
>
> So I am thinking that either there is something wrong with my 356
> board that is causing this noise or perhaps their is an issue with
> the cable routing (perhaps maybe it shouldn't be bundled with a
> power cable or something).
>
> Thanks,
> Chase
>
>
>
>
>

Cool.  Thanks Florain

--- On Wed, 2/12/09, Florian Anwander <fanwander@mnet-online.de> wrote:

From: Florian Anwander <fanwander@mnet-online.de>
Subject: Re: [korg_mono-poly] Re: Mono/Poly doesn't turn on. (Transformer gets really hot)
To: korg_mono-poly@yahoogroups.com
Date: Wednesday, 2 December, 2009, 10:11

 

Alan Dicker schrieb:
>
>
> It could maybe be a Op Amp on that is leaking some timer data in to the
> signel path. Haven't get scimatics or anything in front of me now

http://fa.utfs. org/diy/korg_ monopoly/ index.html

> but could be worth checking the outputs on any Op Amp assoctiated with the Arp.
There are two connections from/to the arpeggiator (which is +5V
circuitry) to the OpAmp-World (which is +/-15V circuitry): The
arpeggiator resets the MG1.
MG1 feeds the Arpeggio Trigger in and the Arpeggio-Switche reset the MG1.
Since the signal at the osci is described like an cyclic enabled adress
line, I think the second option should be the suspected one. It might be
worth to interrupt this connection. It is the wire from LFO-Board
connector 6 pin 10 to uP-board connector 23 pin 10.

Btw: this is a modification I'd recommend anyway, if you do not want to
reset the arp-Clock with every new chord, that you play.

Florian

>
> --- On *Wed, 2/12/09, plus_321 /<plus_321@yahoo. com>/* wrote:
>
>
> From: plus_321 <plus_321@yahoo. com>
> Subject: [korg_mono-poly] Re: Mono/Poly doesn't turn on.
> (Transformer gets really hot)
> To: korg_mono-poly@ yahoogroups. com
> Date: Wednesday, 2 December, 2009, 8:23
>
>
>
>
> I tried to use an oscilloscope today to check the power rails. I
> check them on the 356 board, but the seemed fine and I could see any
> significant fluctuations.
>
> I realize that when I unplug the VCA out connector or power input on
> the VCF board then the noise becomes much louder. So I was able to
> put the scope on the output and see what it looks like. It appears
> to be a constant frequency pulse wave with a small cycle length,
> like 5-10%. The noise doesn't go through the filter so it isn't
> oscillator bleed and it doesn't track the keyboard. The only thing
> that really affects it is moving the arp switches.
>
> I've found the noise goes away completely if I unplug the arp
> connector from the 356 board, but if I unplug the same cable from
> the other end, the noise remains, but is reduced in volume. I
> checked the cable and it seems good.
>
> So I am thinking that either there is something wrong with my 356
> board that is causing this noise or perhaps their is an issue with
> the cable routing (perhaps maybe it shouldn't be bundled with a
> power cable or something).
>
> Thanks,
> Chase
>
>
>
>
>

Just a short (late) reply to tell everyone that the transfo used in most MP4 is running quite hot after a an hour or more of use. It is the result of Korg putting a 1.2 amp tranfo in a synth that consumes... 1.2 amps! So that part is working in the proximity of its maximum tolerance, and thus dissipates about 30 watts of heat. But that transfo is of high quality and should be able to handle that kind of heat easily. So I wouldn't worry about that. But no part is infallible and it could still fail.

Alain.

--- In korg_mono-poly@yahoogroups.com, "plus_321" <plus_321@...> wrote:
>
> Hello.
>
> Just a few moments ago I was playing some music and all of a sudden my mono/poly stopped working. I tried to flip the switch and nothing happens; no lights or sound. (I didn't see or smell smoke)
>
> I opened it up and the fuses are all fine, but the transformer was so hot that I couldn't keep my finger on it for more than a moment (even now, 15 minutes later it is still very warm).
> I used the service manual and checked on board 356 for voltages and none of them registered(5, 15, or -15).
>
> I'm not sure what to do now. I'm guessing the transformer died, but how can I know for sure? What would cause the transformer to just go out like that? If it is the transformer, does anyone here have a spare or know where to find one?
>
> Thanks,
> Chase
>