Korg Poly 800 problem joystick DCO e VCF not working

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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby Faldoe » Mon Mar 23, 2015 5:11 am

Weirdofromouterspace wrote:Hi veraferro,

veraferro wrote:I have altered in a way and maybe that's why it does not work ..

Image


erm... you might try to install the capacitor with correct polarity ;) .

veraferro wrote:but I noticed in the second picture that you have also installed two resistors, right?


No, I didn't add any resistors. Do you mean the ones on top of R18 and R20? They were there when I got the synth...

Possibly the previous owner did this to lower the resistor value according to 1/R(total) = 1/R(1) + 1/R(2)...

It can, if at all, only be a minor change, imho.



Hi, I tried this mod and I'm getting no sound out of my Poly 800.

As I understand the mod, given your description:

Green wire (outer switch lug) to Pin 5 on IC, Red wire (outer switch lug) to Pin 6 on IC.

Negative of Electro Cap to switch center lug, Positive side of Cap to C103 Positive on the PCB. - I'm going by what you suggested to Veraferro in his drawing, as you said to get the polarity right...

Is that correct?
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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby Weirdofromouterspace » Mon Mar 23, 2015 9:06 am

Faldoe wrote:Green wire (outer switch lug) to Pin 5 on IC, Red wire (outer switch lug) to Pin 6 on IC.

Negative of Electro Cap to switch center lug, Positive side of Cap to C103 Positive on the PCB. - I'm going by what you suggested to Veraferro in his drawing, as you said to get the polarity right...

Is that correct?


Sounds right to me. The color of the wire is of course not important ;-).
Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you get no sound out of it. - ARP 2600 manual, 1971
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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby veraferro » Mon Mar 23, 2015 4:32 pm

Weirdofromouterspace wrote:
Sounds right to me. The color of the wire is of course not important ;-).





hello Weirdofromouterspace,
I finally solved the problem 12/24 db ..
now everything ok, 12/24 db works perfectly ..

the problem remains on the joystick, still not able to solve, I can not figure out which manages the integrated joystick. according to you which IC should I replace?
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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby Faldoe » Tue Mar 24, 2015 12:57 am

Weirdofromouterspace wrote:
Faldoe wrote:Green wire (outer switch lug) to Pin 5 on IC, Red wire (outer switch lug) to Pin 6 on IC.

Negative of Electro Cap to switch center lug, Positive side of Cap to C103 Positive on the PCB. - I'm going by what you suggested to Veraferro in his drawing, as you said to get the polarity right...

Is that correct?


Sounds right to me. The color of the wire is of course not important ;-).


Haha, yes, I know the wire color isn't important but I happened to have the same colors and figured it would be that much easier to just follow what you did.

I'll reverse the mod and see if that does anything.

Does the Negative pad on the PCB for C103 need to be hooked up to anything? I see in your picture the cap wire just goes to the Positive pad on the PCB.

EDIT*** I removed the mod and the keyboard works again.

Does the switch need to be center off? I'm assuming not, I'm using a regular SPST switch.

I tried to install the mod again, and again; no sound.
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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby Weirdofromouterspace » Tue Mar 24, 2015 8:57 am

veraferro wrote:I finally solved the problem 12/24 db ..
now everything ok, 12/24 db works perfectly ..


=D>

veraferro wrote:the problem remains on the joystick, still not able to solve, I can not figure out which manages the integrated joystick. according to you which IC should I replace?


I haven't dealt with the joystick yet, so let's use the ask the audience joker ;).
Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you get no sound out of it. - ARP 2600 manual, 1971
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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby Weirdofromouterspace » Tue Mar 24, 2015 9:10 am

Faldoe wrote:Does the Negative pad on the PCB for C103 need to be hooked up to anything?


No. It is originally connected directly to pin 6. All the mod does is disconnect this direct connection and insert the switch.

I'll try to illustrate it as follows:

original: (C103(-)) --> pin 6

mod: (C103(-)) --> switch --> either pin 6 or pin 5

Faldoe wrote:EDIT*** I removed the mod and the keyboard works again.
[...] I tried to install the mod again, and again; no sound.


Check all connections you made, and all polarities wherever applicable. Be sure you connected the correct pins of the filter IC - it is easy to accidentally connect, say, 4 and 5 instead of 5 and 6... ;)

Faldoe wrote:Does the switch need to be center off?


No, a simple on/on switch will do. There is even a variation of this mod that uses a potentiometer instead of a switch, allowing you to blend 12 and 24 dB/oct filters.
Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you get no sound out of it. - ARP 2600 manual, 1971
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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby Faldoe » Tue Mar 24, 2015 7:02 pm

Weirdofromouterspace wrote:
Faldoe wrote:Does the Negative pad on the PCB for C103 need to be hooked up to anything?


No. It is originally connected directly to pin 6. All the mod does is disconnect this direct connection and insert the switch.

I'll try to illustrate it as follows:

original: (C103(-)) --> pin 6

mod: (C103(-)) --> switch --> either pin 6 or pin 5

Faldoe wrote:EDIT*** I removed the mod and the keyboard works again.
[...] I tried to install the mod again, and again; no sound.


Check all connections you made, and all polarities wherever applicable. Be sure you connected the correct pins of the filter IC - it is easy to accidentally connect, say, 4 and 5 instead of 5 and 6... ;)

Faldoe wrote:Does the switch need to be center off?


No, a simple on/on switch will do. There is even a variation of this mod that uses a potentiometer instead of a switch, allowing you to blend 12 and 24 dB/oct filters.



I'm definitely on the right Pins - followed your pictured, and minded the corrected side of the chip.

So there is no connection that goes to the Negative pad on C103?

There doesn't need to be a jumper. From what I follow in the bolded part of your quote above is that the Negative of C103 goes to the switch - you're taking about the Capacitor and not the pad, right?

It shouldn't matter which outer wire on the switch goes to 5 or 6, right? As long as one goes to each, it should be fine, yes?

I used a new 10uf Electro cap and I used the old one just in case there was an issue and still no luck.

I put the new 10uf cap (by itself) on the C103 PCB position and the synth works again. So I'm lost. It has to be something simple.

Can you give a schematic drawing - doesn't need to be detailed. I'm just more visually inclined.
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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby Weirdofromouterspace » Wed Mar 25, 2015 10:11 am

Faldoe wrote:So there is no connection that goes to the Negative pad on C103?


No there isn't. The direct connection to pin 6 is replaced by the switch and wires. That's what the mod is about.

Faldoe wrote:the Negative of C103 goes to the switch - you're taking about the Capacitor and not the pad, right?


Yes. You can see in one of my pictures how the capacitor is soldered directly to the switch. The (+) end of the capacitor is connected by a wire to the (+) pad on the PCB, simply because the capacitor is now too far away from the PCB.

Faldoe wrote:It shouldn't matter which outer wire on the switch goes to 5 or 6, right? As long as one goes to each, it should be fine, yes??


Yes, of course. That only affects to which position you have to throw the switch to select 12 or 24 dB/oct.

Faldoe wrote:I put the new 10uf cap (by itself) on the C103 PCB position and the synth works again. So I'm lost. It has to be something simple.


Be sure the capacitor is soldered to the switch and the (+) wire with correct polarity.
Did you check your switch isn't faulty? That can and does happen, y'know...

Faldoe wrote:Can you give a schematic drawing


I already did. Check out the link to Muffwigglers in this post:
viewtopic.php?p=745537#p745537
Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you get no sound out of it. - ARP 2600 manual, 1971
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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby Faldoe » Sun Apr 05, 2015 10:53 pm

I put the cap lead to the negative pad of C103 and the mod seems to work, I don't know why that is...
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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby kogz23 » Mon May 25, 2015 6:38 am

Hi there,
I had the same problem with the joystick controlling the pitch and vcf/dco mod simultaneously. I found IC16 to be the problem. It was driving me crazy and this fixed it for me. Hope this helps!
Cheers
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Re: Korg Poly 800 problem joystick DCO e VCF not working

Postby enzino » Mon Aug 29, 2016 12:46 am

I put the cap lead to the negative pad of C103 and the mod seems to work, I don't know why that is...

of course, that's the correct way
in the previous pics there is a mistake: in the original circuit the signal comes from the VCF (2069 pin 6),
enter in C103+ and from C103- goes to the Chorus board, if you desolder C103 a tester can confirm that
pin 6 of 2069 is connected directly to C103+, so the correct way to do the mod is: pin5 and pin6 to the two
sides of the switch, the center of this soldered to + of the cap and from the cap to - on the board

sorry for my poor english, I'm italian
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