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Poly-800 short-circuit damage diagnosis.

Poly-800 short-circuit damage diagnosis.

2011-08-03 by 7yash

Ow, I noticed something wrong with the sounds of the Poly-800 yesterday and thought I could fix it with a transfer of the sounds from the computer again, but no!

Inside, I understood what went wrong, at least the cause: a screw was moving around on the main board and has most probably caused a short...

Results:
1. When the Cutoff Frequency knob is turned to min, there is a swooshing sound as if the Cutoff is being modulated (even if I turn MG off)...

2. Sounds thin out on some keys, but sometimes the keys get their volume up again after playing other keys...

The oscillators seem fine (doesn't help, I don't really care about them :P )

What should I verify or fix?

Needless to say, it's a bit disheartening after all the successful mods I made and their ergonomic placement ;) and right before I was embarking on what could have been the best mod ever.

Help!

Re: [korgpolyex] Poly-800 short-circuit damage diagnosis.

2011-08-03 by billmeirelles@uol.com.br

Does it sound like the mp3 I posted?
The one called VCF_DRIFT_PROBLEM.mp3

Em 03/08/2011 17:03, 7yash < josh.nursing@... > escreveu:

Ow, I noticed something wrong with the sounds of the Poly-800 yesterday and thought I could fix it with a transfer of the sounds from the computer again, but no!

Inside, I understood what went wrong, at least the cause: a screw was moving around on the main board and has most probably caused a short...

Results:
1. When the Cutoff Frequency knob is turned to min, there is a swooshing sound as if the Cutoff is being modulated (even if I turn MG off)...

2. Sounds thin out on some keys, but sometimes the keys get their volume up again after playing other keys...

The oscillators seem fine (doesn't help, I don't really care about them :P )

What should I verify or fix?

Needless to say, it's a bit disheartening after all the successful mods I made and their ergonomic placement ;) and right before I was embarking on what could have been the best mod ever.

Help!



Re: [korgpolyex] Re: Poly-800 short-circuit damage diagnosis.

2011-08-03 by billmeirelles@uol.com.br

I see, ol, sorry I have no clue...
The best choice is to test the parts one by one following the tracks,
same thing I'll have to do to find where's the extra voltage coming
from.


Em 03/08/2011 18:02, 7yash < josh.nursing@... > escreveu:

No it doesn't sound intermittent like that: on min Cutoff, there's a type of LFO to it.

Also, some keys sound faint at some points.


Re: [korgpolyex] Re: Poly-800 short-circuit damage diagnosis.

2011-08-03 by billmeirelles@uol.com.br

Take the pin for VCF CV INPUT in the NJM and follow the tracks backwards.
Set EG3 and LFO to VCF int to 0. Now send a sustained midi note from a
sequencer and make it loop, then using a meter you should mesure a voltage
variation at the NJM pin and as you move backwards at some point the variation
will stop and you should get a stable voltage, this point is probably the cause
of the problem, then you must test the part in between the 2 points to see
if it's fried, my guess is it's a bad transistor or you managed to fry the NJM input.


Em 03/08/2011 18:43, 7yash < josh.nursing@... > escreveu:

That's what I thought too.

Except: how do I know what voltages I should look for?


Re: Poly-800 short-circuit damage diagnosis.

2011-08-03 by 7yash

Oh yes, the joystick could be malfunctioning and not zeroing correctly.

However, this does not explain the keys issue.

Still, I'll check it. Thanks, Bill.

Will try to follow the metering along the circuit path and see what happens.

Re: Poly-800 short-circuit damage diagnosis.

2011-08-03 by 7yash

Great, this gives me a starting point to work from! Thanks.

Hope I didn't fry the NJM2069 inputs - that would be a shame.

On the other hand, I have an SSM2044 and 8 CEM3079 and a CEM3360 to work with ;)

Re: Poly-800 short-circuit damage diagnosis.

2011-08-03 by 7yash

Found it!

It seems something is loose around the FM-800 pot, that's all, so the NJM2609 is fine and dandy.

Bill, I certainly would have checked that same section/mod too.

I also found a loose joint in the Resonance pot, so the soldering iron is back on the mains.

--- In korgpolyex@yahoogroups.com, "7yash" <josh.nursing@...> wrote:
>
> Oh yes, the joystick could be malfunctioning and not zeroing correctly.
>
> However, this does not explain the keys issue.
>
> Still, I'll check it. Thanks, Bill.
>
> Will try to follow the metering along the circuit path and see what happens.
>

Re: [korgpolyex] Re: Poly-800 short-circuit damage diagnosis.

2011-08-03 by billmeirelles@uol.com.br

Yep, mine seems to be just the CUTOFF pot of the moog slayer mod
that got dirty, I'm cleaning it with isopropyl right now...


Em 03/08/2011 20:08, 7yash < josh.nursing@... > escreveu:

Found it!

It seems something is loose around the FM-800 pot, that's all, so the NJM2609 is fine and dandy.

Bill, I certainly would have checked that same section/mod too.

I also found a loose joint in the Resonance pot, so the soldering iron is back on the mains.

--- In korgpolyex@yahoogroups.com, "7yash" wrote:
>
> Oh yes, the joystick could be malfunctioning and not zeroing correctly.
>
> However, this does not explain the keys issue.
>
> Still, I'll check it. Thanks, Bill.
>
> Will try to follow the metering along the circuit path and see what happens.
>


Re: Poly-800 short-circuit damage diagnosis.

2011-08-04 by 7yash

Hi Achim, have you checked your Yahoo Group registration settings for this group? YOu should be able to change it to plain text.

Also, I was reading some of your posts on Synth-DIY about Walsh functions just this morning!

I'm in the process of exploring how much of missing Walsh harmonics I could re-generate from the Poly-800 and if it would be worthwhile.

Because basically, the MSM5232 emits Rademacher signals without the #1 order signal and I should be able to fill in the sound with a bunch of XORs.

Yash

--- In korgpolyex@yahoogroups.com, ASSI <Stromeko@...> wrote:
> On Thursday 04 August 2011, billmeirelles@... wrote:
> Bill, could you please send plain text instead of HTML mails to this list?
> Regards,
> Achim.

Re: [korgpolyex] Re: Poly-800 short-circuit damage diagnosis.

2011-08-04 by ASSI

On Thursday 04 August 2011, 7yash wrote:
> Hi Achim, have you checked your Yahoo Group registration settings for
> this group? YOu should be able to change it to plain text.

As a matter of fact, I already did that years ago. Bill's mails are the
only ones I get as HTML and he did send two or three inbetween as plain
text, so I think the configuration error is at his end (he seems to send in
HTML _only_ most of the time).

> Also, I was reading some of your posts on Synth-DIY about Walsh functions
> just this morning!
>
> I'm in the process of exploring how much of missing Walsh harmonics I
> could re-generate from the Poly-800 and if it would be worthwhile.

Reminds me I have an unfinished writeup on Walsh synthesis lying around.

> Because basically, the MSM5232 emits Rademacher signals without the #1
> order signal and I should be able to fill in the sound with a bunch of
> XORs.

Walsh synthesis is a control problem, just like additive synthesis in
general. You can stick a bunch of XOR on a divider and get some more waves
out of it no problem, but then you need to control their amplitudes somehow
and that is where things get complicated.


Regards,
Achim.
--
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

SD adaptation for Waldorf rackAttack V1.04R1:
http://Synth.Stromeko.net/Downloads.html#WaldorfSDada

Re: Poly-800 short-circuit damage diagnosis.

2011-08-04 by 7yash

Odd fr those settings, but I do know Yahoo Groups have updated their settings. If nothing works try a leave group/join group and see the settings then.

On Walsh:

--- In korgpolyex@yahoogroups.com, ASSI <Stromeko@...> wrote:
> Walsh synthesis is a control problem, just like additive synthesis in
> general. You can stick a bunch of XOR on a divider and get some more waves
> out of it no problem, but then you need to control their amplitudes somehow
> and that is where things get complicated.

Yes, precisely, a control problem (as any form of 'additive' like Fourier) and therefore where the opportunities to improve the Osc section of the Poly-800 lie!

So, initially, after I re-create the missing Walsh orders, I would want to simply manually alter or LFO their amplitudes i the mix before mixing them back into the DCOx Mix signal In.

Later, if I can get that under micro-controller control (like an Arduino), that owuld be fair game too.

For now, the plan about reading on Walsh, Rademacher and so on is just fitting into the larger goal of improving that OSC section, which is rather dire as is.

Any suggestions are welcome.

Re: Poly-800 short-circuit damage diagnosis.

2011-08-04 by 7yash

On second thought, Y Groups also allow replying from your mail client, so that's where the issue is I believe.

--- In korgpolyex@yahoogroups.com, ASSI <Stromeko@...> wrote:
> As a matter of fact, I already did that years ago. Bill's mails are the
> only ones I get as HTML and he did send two or three inbetween as plain
> text, so I think the configuration error is at his end (he seems to send in
> HTML _only_ most of the time).

Re: [korgpolyex] Re: Poly-800 short-circuit damage diagnosis.

2011-08-05 by billmeirelles@uol.com.br

Sorry if my e-mails are in HTML and you don't like it, I can't see the point,
anyways I'm just replying the e-mails I received in my mail box, I'm not sure
if I can change the way my webmail sends it, I belive I can't... the message
that you received from me in plain text was probably the one I've posted
in group page directly...


Em 04/08/2011 15:31, ASSI < Stromeko@... > escreveu:

On Thursday 04 August 2011, 7yash wrote:
> Hi Achim, have you checked your Yahoo Group registration settings for
> this group? YOu should be able to change it to plain text.

As a matter of fact, I already did that years ago. Bill's mails are the
only ones I get as HTML and he did send two or three inbetween as plain
text, so I think the configuration error is at his end (he seems to send in
HTML _only_ most of the time).

> Also, I was reading some of your posts on Synth-DIY about Walsh functions
> just this morning!
>
> I'm in the process of exploring how much of missing Walsh harmonics I
> could re-generate from the Poly-800 and if it would be worthwhile.

Reminds me I have an unfinished writeup on Walsh synthesis lying around.

> Because basically, the MSM5232 emits Rademacher signals without the #1
> order signal and I should be a ble to fill in the sound with a bunch of
> XORs.

Walsh synthesis is a control problem, just like additive synthesis in
general. You can stick a bunch of XOR on a divider and get some more waves
out of it no problem, but then you need to control their amplitudes somehow
and that is where things get complicated.

Regards,
Achim.
--
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

SD adaptation for Waldorf rackAttack V1.04R1:
http://Synth.Stromeko.net/Downloads.html#WaldorfSDada


Re: [korgpolyex] Re: Poly-800 short-circuit damage diagnosis.

2011-08-05 by billmeirelles@uol.com.br

Exactly, that's what I do, if HTML is too much of a problem I'll configure
my account to stop sending the messages to my e-mail but unfortunately
I'll have to stop answering the messages too cause I don't have time to
login to another account everyday, I just login to my e-mail and let the
computer running all day long to receive my messages, sory but I don't
have spare time to become a computer sitter...

Em 04/08/2011 15:58, 7yash < josh.nursing@... > escreveu:

On second thought, Y Groups also allow replying from your mail client, so that's where the issue is I believe.

--- In korgpolyex@yahoogroups.com, ASSI wrote:
> As a matter of fact, I already did that years ago. Bill's mails are the
> only ones I get as HTML and he did send two or three inbetween as plain
> text, so I think the configuration error is at his end (he seems to send in
> HTML _only_ most of the time).


Re: Poly-800 short-circuit damage diagnosis.

2011-08-05 by 7yash

Don't do that Bill,

Keep the email into the inbox, but then when you get a message from Yahoo Groups, go down to the message and click "Reply by web post". It will bring you to the Y G web page.

Regards.