Korg Mono/Poly

I just recently moved to Japan from the Seattle area and brought a couple treasured items along to create with, the Mono/Poly being one of them. So today, I was recording with the MonoPoly playing in poly mode while adjusting the filter and the sound very quickly faded out. No nothing from any of the oscillators the filter or the noise gen. I can however hear a very quiet sound of maybe the ADSR when I play the keys. Just so all possible information is present I want to also note that I was powering it through a newly purchased step up transformer (not sure if that could have had any effect on my precious)


I also have a couple keys that don't work -it's not just dirty contacts either. It looks like the contacts for those keys are corroded somehow. Is it possible to find or repair the contact board?

Please, any help would be greatly appreciated!

thank you,
chad

From: likeandrot <likeandrot@yahoo.com>
Subject: [korg_mono-poly] ...and all of the sudden, no sound!
To: korg_mono-poly@yahoogroups.com
Date: Thursday, 27 May, 2010, 11:11

 

I just recently moved to Japan from the Seattle area and brought a couple treasured items along to create with, the Mono/Poly being one of them. So today, I was recording with the MonoPoly playing in poly mode while adjusting the filter and the sound very quickly faded out. No nothing from any of the oscillators the filter or the noise gen. I can however hear a very quiet sound of maybe the ADSR when I play the keys. Just so all possible information is present I want to also note that I was powering it through a newly purchased step up transformer (not sure if that could have had any effect on my precious)

I also have a couple keys that don't work -it's not just dirty contacts either. It looks like the contacts for those keys are corroded somehow. Is it possible to find or repair the contact board?

Please, any help would be greatly appreciated!

thank you,
chad

Hi Alan

> From your description it sounds like you filter chip SSM2044 may have
> gone.

first he should check whether there is a signal at pin 1 (input) of the
SSM2044
Also it is worth checking the four ICs 2033 at pin 8, 3 and 12 whether
there is a signal.

> mean it seems that the rubber contact has corroded or the PCB contact?
> You night find the rubber strips on ebay. same type as in the polysix
> and another few keyboards. as for finding a complete keyboard PCB that
> might be more tricky.

check also http://www.oldcrows.net/~oldcrow/synth/korg/polysix/keyclean.html

If the contacts don't work ever, then maybe also some of the diodes in
the keyboard matrix might have died.

Florian

From: chad imes <likeandrot@yahoo.com>
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
To: korg_mono-poly@yahoogroups.com
Date: Thursday, 27 May, 2010, 13:18

 

it's the PCB that's corroded somehow -like the previous owner spilt a soft drink on it or something?

Soooo, is it possible to check these things using a DMM?  0_o  That's all I got.

thanks again,

chad

From: Florian Anwander <fanwander@mnet- online.de>
To: korg_mono-poly@ yahoogroups. com
Sent: Thu, May 27, 2010 8:39:38 PM
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!

 

Hi Alan

> From your description it sounds like you filter chip SSM2044 may have
> gone.
first he should check whether there is a signal at pin 1 (input) of the
SSM2044
Also it is worth checking the four ICs 2033 at pin 8, 3 and 12 whether
there is a signal.

> mean it seems that the rubber contact has corroded or the PCB contact?
> You night find the rubber strips on ebay. same type as in the polysix
> and another few keyboards. as for finding a complete keyboard PCB that
> might be more tricky.
check also http://www.oldcrows .net/~oldcrow/ synth/korg/ polysix/keyclean .html

If the contacts don't work ever, then maybe also some of the diodes in
the keyboard matrix might have died.

Florian

"...I want to also note that I was powering it through a newly purchased
step up transformer..."

Japan's household power is 100v A.C. if I'm not mistaken. Your step up transformer is listed as what ? 100v to 120v A.C. ? If it says anything else, like 120v to 240V then it will certainly damage your MP4.

Also, it sounds very much like your SSM2044 has died. In case this would also happen to me, I've purchased a replacement recently on an Ebay store in China for about $10 (including shipping!). It arrived quickly and in perfect condition and is now in my MP4 working fine, the date stamp is 1987. I have kept the original (date stamp 1982) as a back-up now.

These chips are 28 years old after all, and they were manufactured in an era where reliability rates were quite low. I'm surprised that they've lasted that long ! I only hope none of the SSM2033 in my MP4 dies, because these chips are impossible to find, unless taken from another non-working MP4.

Good luck.
Alain.

--- In korg_mono-poly@yahoogroups.com, "likeandrot" <likeandrot@...> wrote:
>
> I just recently moved to Japan from the Seattle area and brought a couple treasured items along to create with, the Mono/Poly being one of them. So today, I was recording with the MonoPoly playing in poly mode while adjusting the filter and the sound very quickly faded out. No nothing from any of the oscillators the filter or the noise gen. I can however hear a very quiet sound of maybe the ADSR when I play the keys. Just so all possible information is present I want to also note that I was powering it through a newly purchased step up transformer (not sure if that could have had any effect on my precious)
>
>
> I also have a couple keys that don't work -it's not just dirty contacts either. It looks like the contacts for those keys are corroded somehow. Is it possible to find or repair the contact board?
>
> Please, any help would be greatly appreciated!
>
> thank you,
> chad
>

This is who I bought a replacement SSM2044 from. Excellent Ebayer.

http://cgi.ebay.com/1-x-IC-Chip-SSM2044-4-Pole-Voltage-Controlled-DIP-16pin-/180393142562?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item2a0044e922

--- In korg_mono-poly@yahoogroups.com, "likeandrot" <likeandrot@...> wrote:
>
> I just recently moved to Japan from the Seattle area and brought a couple treasured items along to create with, the Mono/Poly being one of them. So today, I was recording with the MonoPoly playing in poly mode while adjusting the filter and the sound very quickly faded out. No nothing from any of the oscillators the filter or the noise gen. I can however hear a very quiet sound of maybe the ADSR when I play the keys. Just so all possible information is present I want to also note that I was powering it through a newly purchased step up transformer (not sure if that could have had any effect on my precious)
>
>
> I also have a couple keys that don't work -it's not just dirty contacts either. It looks like the contacts for those keys are corroded somehow. Is it possible to find or repair the contact board?
>
> Please, any help would be greatly appreciated!
>
> thank you,
> chad
>

--- On Fri, 28/5/10, chad imes <likeandrot@yahoo.com> wrote:

From: chad imes <likeandrot@yahoo.com>
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
To: korg_mono-poly@yahoogroups.com
Date: Friday, 28 May, 2010, 0:21

 

thanks Alan and Florian!

I'll take pictures of the PCB so you can see.  

One point I'm still not clear on is how I might test the output of the SSM 2044 and the 2033s.  Can that be done with a DMM or in another easy cheap way?

thank you very very much!!!

chad 

From: Alan Dicker <alanmdicker@ yahoo.co. uk>
To: korg_mono-poly@ yahoogroups. com
Sent: Thu, May 27, 2010 11:09:43 PM
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!

 

got any pictures?  it may be that the pads have carodid to the piont wher the metirial don;t conduct properley or it might be just that the surface is to uneaven to give good contact over the the pad.  testing the curcuit by simply holding a wier over the connection in place of the rubber pad might help you determin of the pads non conductive any more but as Florain said it may be the associated diode thats faild.  those diodes are very cheap parts to get.

 

I take it the board and rubber contacts have all been cleaned in the past?

 

--- On Thu, 27/5/10, chad imes <likeandrot@yahoo. com> wrote:

From: chad imes <likeandrot@yahoo. com>
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
To: korg_mono-poly@ yahoogroups. com
Date: Thursday, 27 May, 2010, 13:18

 

it's the PCB that's corroded somehow -like the previous owner spilt a soft drink on it or something?

Soooo, is it possible to check these things using a DMM?  0_o  That's all I got.

thanks again,

chad

From: Florian Anwander <fanwander@mnet- online.de>
To: korg_mono-poly@ yahoogroups. com
Sent: Thu, May 27, 2010 8:39:38 PM
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!

 

Hi Alan

> From your description it sounds like you filter chip SSM2044 may have
> gone.
first he should check whether there is a signal at pin 1 (input) of the
SSM2044
Also it is worth checking the four ICs 2033 at pin 8, 3 and 12 whether
there is a signal.

> mean it seems that the rubber contact has corroded or the PCB contact?
> You night find the rubber strips on ebay. same type as in the polysix
> and another few keyboards. as for finding a complete keyboard PCB that
> might be more tricky.
check also http://www.oldcrows .net/~oldcrow/ synth/korg/ polysix/keyclean .html

If the contacts don't work ever, then maybe also some of the diodes in
the keyboard matrix might have died.

Florian

Hello Alan

> Many might disagree with me her and I would like to say be very careful
> while working this way but I often find that if no oscilloscope is
> available that simply testing the signal path with a wire attached to
> the tip of an audio jack will tell you allot.

I do this all the time, the way you are describing (and I think most
technicians do it that way). Use only extremely simple speakers or
headphones for this, because there may signal transitions happen, which
can kill tweeters or delicate headphones! I have a set of old car hifi
speakers on my workbench for this.

Florian

Good to know Im not alone

--- On Fri, 28/5/10, Florian Anwander <fanwander@mnet-online.de> wrote:

From: Florian Anwander <fanwander@mnet-online.de>
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
To: korg_mono-poly@yahoogroups.com
Date: Friday, 28 May, 2010, 10:32

 

Hello Alan

> Many might disagree with me her and I would like to say be very careful
> while working this way but I often find that if no oscilloscope is
> available that simply testing the signal path with a wire attached to
> the tip of an audio jack will tell you allot.
I do this all the time, the way you are describing (and I think most
technicians do it that way). Use only extremely simple speakers or
headphones for this, because there may signal transitions happen, which
can kill tweeters or delicate headphones! I have a set of old car hifi
speakers on my workbench for this.

Florian

From: chad imes <likeandrot@yahoo.com>
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
To: korg_mono-poly@yahoogroups.com
Date: Wednesday, 9 June, 2010, 10:14

 

so per your fine advice I didn't even test anything I just went straight to replacing the 2044 (there was already a socket installed) and now my darling analogue princess sings again!

thank you so much!!!!

From: Alan Dicker <alanmdicker@ yahoo.co. uk>
To: korg_mono-poly@ yahoogroups. com
Sent: Fri, May 28, 2010 5:55:44 PM
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!

 

One thing to test is can your filter self oscillate with the res right up?  the resonance feedback is all on chip with the 2044 so if it can do that your chip is bad.

 

A digital multi meter wont really cut it re testing the correct tool to use is an Oscilloscope.

If you don have one of those....

 

try bellow methods at your own risk.

 

Many might disagree with me her and I would like to say be very careful while working this way but I often find that if no oscilloscope is available that simply testing the signal path with a wire attached to the tip of an audio jack will tell you allot.

it is a rather gorilla method and you need steady hands to work this way as if you touch or short out something you shouldn't it could cost you allot more than a SSM 2044.

 

Audio comes in to pin 1 of the 2044.  if you follow this trace from pin one to the first resistor leg it meets you can hold your wire there and see if you here anything?  I would recommend having your monopoly arps running in poly mode so you don't have to hit the keys your self.

Also remember that the signal level at this point will be quite different from the final output stage.  most likely allot higher so start with the level of your gear quite low to safe guard your speakers and amp.

you should here un-filtered VCOs.

pin 3 is the audio out.  test here with the same method.  if your chip were working you would here something if not your chip is dead.  I suspect the chip is dead anyway.  with a dead chip you would still here a slight noise of the final amp envelope open and close when monitoring at high volume as this stage comes after the filter.

 

remember though 2044s are cheap to get comped to allot of SSM chips so its really worth getting a few installing a socket and swapping out the old one rather than poking around and causing more damage.

--- On Fri, 28/5/10, chad imes <likeandrot@yahoo. com> wrote:

From: chad imes <likeandrot@yahoo. com>
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
To: korg_mono-poly@ yahoogroups. com
Date: Friday, 28 May, 2010, 0:21

 

thanks Alan and Florian!

I'll take pictures of the PCB so you can see.  

One point I'm still not clear on is how I might test the output of the SSM 2044 and the 2033s.  Can that be done with a DMM or in another easy cheap way?

thank you very very much!!!

chad 

From: Alan Dicker <alanmdicker@ yahoo.co. uk>
To: korg_mono-poly@ yahoogroups. com
Sent: Thu, May 27, 2010 11:09:43 PM
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!

 

got any pictures?  it may be that the pads have carodid to the piont wher the metirial don;t conduct properley or it might be just that the surface is to uneaven to give good contact over the the pad.  testing the curcuit by simply holding a wier over the connection in place of the rubber pad might help you determin of the pads non conductive any more but as Florain said it may be the associated diode thats faild.  those diodes are very cheap parts to get.

 

I take it the board and rubber contacts have all been cleaned in the past?

 

--- On Thu, 27/5/10, chad imes <likeandrot@yahoo. com> wrote:

From: chad imes <likeandrot@yahoo. com>
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
To: korg_mono-poly@ yahoogroups. com
Date: Thursday, 27 May, 2010, 13:18

 

it's the PCB that's corroded somehow -like the previous owner spilt a soft drink on it or something?

Soooo, is it possible to check these things using a DMM?  0_o  That's all I got.

thanks again,

chad

From: Florian Anwander <fanwander@mnet- online.de>
To: korg_mono-poly@ yahoogroups. com
Sent: Thu, May 27, 2010 8:39:38 PM
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!

 

Hi Alan

> From your description it sounds like you filter chip SSM2044 may have
> gone.
first he should check whether there is a signal at pin 1 (input) of the
SSM2044
Also it is worth checking the four ICs 2033 at pin 8, 3 and 12 whether
there is a signal.

> mean it seems that the rubber contact has corroded or the PCB contact?
> You night find the rubber strips on ebay. same type as in the polysix
> and another few keyboards. as for finding a complete keyboard PCB that
> might be more tricky.
check also http://www.oldcrows .net/~oldcrow/ synth/korg/ polysix/keyclean .html

If the contacts don't work ever, then maybe also some of the diodes in
the keyboard matrix might have died.

Florian

Woohoo! Great news! Now, if all repairs could be that simple ?
By the way, mine too had a socket already installed...

You will notice, however, that your beloved MP4 filter might behave a little differently than before. This is due to the fact that each new 2044 replacement, it would ideally require a re-calibration of the filter section to re-adjust for maximum resonance, self-oscillation threshold, full range of the cutoff, maximum level of modulation, and so on... Since each SSM2044 is a linear circuit and they each behave slightly differently.

That being said, it might also behave close enough to your old one and not need any significant re-adjustments. Mine needed to be re-calibrated. Yours might not.

Anyway, the most important thing is: it's alive again !

Alain.

--- In korg_mono-poly@yahoogroups.com, chad imes <likeandrot@...> wrote:
>
> so per your fine advice I didn't even test anything I just went straight to replacing the 2044 (there was already a socket installed) and now my darling analogue princess sings again!
>
> thank you so much!!!!
>
>
>
> ________________________________
> From: Alan Dicker <alanmdicker@...>
> To: korg_mono-poly@yahoogroups.com
> Sent: Fri, May 28, 2010 5:55:44 PM
> Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
>
>
>
> One thing to test is can your filter self oscillate with the res right up? the resonance feedback is all on chip with the 2044 so if it can do that your chip is bad.
>
> A digital multi meter wont really cut it re testing the correct tool to use is an Oscilloscope.
> If you don have one of those....
>
> try bellow methods at your own risk.
>
> Many might disagree with me her and I would like to say be very careful while working this way but I often find that if no oscilloscope is available that simply testing the signal path with a wire attached to the tip of an audio jack will tell you allot.
> it is a rather gorilla method and you need steady hands to work this way as if you touch or short out something you shouldn't it could cost you allot more than a SSM 2044.
>
> Audio comes in to pin 1 of the 2044. if you follow this trace from pin one to the first resistor leg it meets you can hold your wire there and see if you here anything? I would recommend having your monopoly arps running in poly mode so you don't have to hit the keys your self.
> Also remember that the signal level at this point will be quite different from the final output stage. most likely allot higher so start with the level of your gear quite low to safe guard your speakers and amp.
> you should here un-filtered VCOs.
> pin 3 is the audio out. test here with the same method. if your chip were working you would here something if not your chip is dead. I suspect the chip is dead anyway. with a dead chip you would still here a slight noise of the final amp envelope open and close when monitoring at high volume as this stage comes after the filter.
>
> remember though 2044s are cheap to get comped to allot of SSM chips so its really worth getting a few installing a socket and swapping out the old one rather than poking around and causing more damage.
> --- On Fri, 28/5/10, chad imes <likeandrot@yahoo. com> wrote:
>
>
> >From: chad imes <likeandrot@yahoo. com>
> >Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
> >To: korg_mono-poly@ yahoogroups. com
> >Date: Friday, 28 May, 2010, 0:21
> >
> >
> >
> >thanks Alan and Florian!
> >
> >
> >I'll take pictures of the PCB so you can see.
> >
> >
> >One point I'm still not clear on is how I might test the output of the SSM 2044 and the 2033s. Can that be done with a DMM or in another easy cheap way?
> >
> >
> >thank you very very much!!!
> >
> >
> >chad
> >
> >
> >
> ________________________________
> From: Alan Dicker <alanmdicker@ yahoo.co. uk>
> >To: korg_mono-poly@ yahoogroups. com
> >Sent: Thu, May 27, 2010 11:09:43 PM
> >Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
> >
> >
> >got any pictures? it may be that the pads have carodid to the piont wher the metirial don;t conduct properley or it might be just that the surface is to uneaven to give good contact over the the pad. testing the curcuit by simply holding a wier over the connection in place of the rubber pad might help you determin of the pads non conductive any more but as Florain said it may be the associated diode thats faild. those diodes are very cheap parts to get.
> >
> >I take it the board and rubber contacts have all been cleaned in the past?
> >
> >
> >--- On Thu, 27/5/10, chad imes <likeandrot@yahoo. com> wrote:
> >
> >
> >>From: chad imes <likeandrot@yahoo. com>
> >>Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
> >>To: korg_mono-poly@ yahoogroups. com
> >>Date: Thursday, 27 May, 2010, 13:18
> >>
> >>
> >>
> >>it's the PCB that's corroded somehow -like the previous owner spilt a soft drink on it or something?
> >>
> >>
> >>Soooo, is it possible to check these things using a DMM? 0_o That's all I got.
> >>
> >>
> >>thanks again,
> >>chad
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> ________________________________
> From: Florian Anwander <fanwander@mnet- online.de>
> >>To: korg_mono-poly@ yahoogroups. com
> >>Sent: Thu, May 27, 2010 8:39:38 PM
> >>Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
> >>
> >>
> >>Hi Alan
> >>
> >>> From your description it sounds like you filter chip SSM2044 may have
> >>> gone.
> >>first he should check whether there is a signal at pin 1 (input) of the
> >>SSM2044
> >>Also it is worth checking the four ICs 2033 at pin 8, 3 and 12 whether
> >>there is a signal.
> >>
> >>> mean it seems that the rubber contact has corroded or the PCB contact?
> >>> You night find the rubber strips on ebay. same type as in the polysix
> >>> and another few keyboards. as for finding a complete keyboard PCB that
> >>> might be more tricky.
> >>check also http://www.oldcrows.net/~oldcrow/synth/korg/polysix/keyclean.html
> >>
> >>If the contacts don't work ever, then maybe also some of the diodes in
> >>the keyboard matrix might have died.
> >>
> >>Florian
> >>
> >>
> >
> >
>