Discussion about the Korg PolySix synthesizer

Hi, 

Every sixth note I play is louder than the rest. Is this a common
problem? Easy to fix?

Thanks,
TR

sounds like one of the VCA's is busted....  it's not a common problem,
but you've already troubleshot it a bit by knowing it's always the 6th
note.

Has the synth always done this, or is this new behavior?

If you open the top of the synth and power it on, you will see the
voice LEDs light up as you play notes.  Watch them to see which voice
is the loud one.. work from there.  I don't have schematics in front
of me, and it's been forever since I've had mine open.  Somebody else
will probably give you more info.



On Fri, Jan 9, 2009 at 5:55 PM, toerag_man <toerag_man@yahoo.com> wrote:
> Hi,
>
> Every sixth note I play is louder than the rest. Is this a common
> problem? Easy to fix?
>
> Thanks,
> TR
>
>
> ------------------------------------
>
> PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6Yahoo! Groups Links
>
>
>
>



-- 
.sig
-Chromatest J. Pantsmaker
http://www.chromatest.net

It's been that way for a while. Probably since I bought it years ago. I'll check the voice LEDs as you suggested. 
Is it easy to find parts to replace a polysix VCA?

Thanks
TR




________________________________

From: Chromatest J. Pantsmaker <chromatest@azburners.org>
To: PolySix@yahoogroups.com
Sent: Friday, January 9, 2009 8:32:13 PM
Subject: Re: [PolySix] One voice louder than the rest


sounds like one of the VCA's is busted....  it's not a common problem,
but you've already troubleshot it a bit by knowing it's always the 6th
note.

Has the synth always done this, or is this new behavior?

If you open the top of the synth and power it on, you will see the
voice LEDs light up as you play notes.  Watch them to see which voice
is the loud one.. work from there.  I don't have schematics in front
of me, and it's been forever since I've had mine open.  Somebody else
will probably give you more info.

On Fri, Jan 9, 2009 at 5:55 PM, toerag_man <toerag_man@yahoo. com> wrote:
> Hi,
>
> Every sixth note I play is louder than the rest. Is this a common
> problem? Easy to fix?
>
> Thanks,
> TR
>
>
> ------------ --------- --------- ------
>
> PolySix "Digiest" Page: http://www.acc. umu.se/~amber/ Poly6Yahoo! Groups Links
>
>
>
>

-- 
.sig
-Chromatest J. Pantsmaker
http://www.chromate st.net
    


      

[Non-text portions of this message have been removed]

Hi TR,

As suggested by CJP you might have a problem with the VCA circuit. 
The VCA heart is an SSM2056 chip which is at position IC34 on the 
voice board (KLM-366) on the right-hand side with the top panel up. 
As an initial check you could try switching the VCA chips from one 
voice to another as they are socketed and can be removed without 
soldering. There are six in total, one for each voice. If you swap 
one and the problem shifts from one voice to another then this might 
be the issue. However, if you own an osciloscope (or know someone who 
does) I would suggest you check the VCA adjustment in the service 
manual (let me know if you can't find a copy). This involves 
adjustment of pot VR9 and comparing output waveforms. If you find you 
need to replace IC34 I have seen them for sale on eBay or you could 
try my old friend Senso at vintageplanet.nl

Also, the SSM series chips are CMOS based and sensitive to static 
electricity. Make sure you take the precautions to earth yourself 
before handling the internals. Drop us a line if you need any more 
help...

Cheers,
Andy

--- In PolySix@yahoogroups.com, "toerag_man" <toerag_man@...> wrote:

>
> Hi, 
> 
> Every sixth note I play is louder than the rest. Is this a common
> problem? Easy to fix?
> 
> Thanks,
> TR
>

Hi,

IC34 SSM2056 is NOT the VCA but the EG. The VCA is built discretely
by transisotrs Q5, Q6, and buffer amp IC33. Nevertheless IC34, acting
as EG, could be the reason for different levels between voices,
although I dont think that this is rather likely when it works
otherwise. The VCA adjustment may correct or compensate the problem
and it is not necessary to do it with an oscilloscope. If you just
want to set the same level on all voices you can do this with a DVM
in AC setting, provided the DVM has low voltage setting in AC; many
cheapos do only have mains voltage range, though. You can measure at
the headphone output; it has the highest voltage level (several Volts).
OR: use your ears!

Good luck!

Johannes


Andrew Jury wrote:

> Hi TR,
> 
> As suggested by CJP you might have a problem with the VCA circuit. 
> The VCA heart is an SSM2056 chip which is at position IC34 on the 
> voice board (KLM-366) on the right-hand side with the top panel up. 
> As an initial check you could try switching the VCA chips from one 
> voice to another as they are socketed and can be removed without 
> soldering. There are six in total, one for each voice. If you swap 
> one and the problem shifts from one voice to another then this might 
> be the issue. However, if you own an osciloscope (or know someone who 
> does) I would suggest you check the VCA adjustment in the service 
> manual (let me know if you can't find a copy). This involves 
> adjustment of pot VR9 and comparing output waveforms. If you find you 
> need to replace IC34 I have seen them for sale on eBay or you could 
> try my old friend Senso at vintageplanet.nl
> 
> Also, the SSM series chips are CMOS based and sensitive to static 
> electricity. Make sure you take the precautions to earth yourself 
> before handling the internals. Drop us a line if you need any more 
> help...
> 
> Cheers,
> Andy
> 
> --- In PolySix@yahoogroups.com, "toerag_man" <toerag_man@...> wrote:
>> Hi, 
>>
>> Every sixth note I play is louder than the rest. Is this a common
>> problem? Easy to fix?
>>
>> Thanks,
>> TR
>>
> 
> 
> 
> ------------------------------------
> 
> PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6Yahoo! Groups Links
> 
> 
>

--- In PolySix@yahoogroups.com, Johannes Hausensteiner <johau@...> wrote:
>
> Hi,
> 
> IC34 SSM2056 is NOT the VCA but the EG. The VCA is built discretely
> by transisotrs Q5, Q6, and buffer amp IC33. Nevertheless IC34, acting
> as EG, could be the reason for different levels between voices,
> although I dont think that this is rather likely when it works
> otherwise. The VCA adjustment may correct or compensate the problem
> and it is not necessary to do it with an oscilloscope. If you just
> want to set the same level on all voices you can do this with a DVM
> in AC setting, provided the DVM has low voltage setting in AC; many
> cheapos do only have mains voltage range, though. You can measure at
> the headphone output; it has the highest voltage level (several Volts).
> OR: use your ears!
> 
> Good luck!
> 
> Johannes
> 
> 
> Andrew Jury wrote:
> > Hi TR,
> > 
> > As suggested by CJP you might have a problem with the VCA circuit. 
> > The VCA heart is an SSM2056 chip which is at position IC34 on the 
> > voice board (KLM-366) on the right-hand side with the top panel up. 
> > As an initial check you could try switching the VCA chips from one 
> > voice to another as they are socketed and can be removed without 
> > soldering. There are six in total, one for each voice. If you swap 
> > one and the problem shifts from one voice to another then this might 
> > be the issue. However, if you own an osciloscope (or know someone who 
> > does) I would suggest you check the VCA adjustment in the service 
> > manual (let me know if you can't find a copy). This involves 
> > adjustment of pot VR9 and comparing output waveforms. If you find you 
> > need to replace IC34 I have seen them for sale on eBay or you could 
> > try my old friend Senso at vintageplanet.nl
> > 
> > Also, the SSM series chips are CMOS based and sensitive to static 
> > electricity. Make sure you take the precautions to earth yourself 
> > before handling the internals. Drop us a line if you need any more 
> > help...
> > 
> > Cheers,
> > Andy
> > 
> > --- In PolySix@yahoogroups.com, "toerag_man" <toerag_man@> wrote:
> >> Hi, 
> >>
> >> Every sixth note I play is louder than the rest. Is this a common
> >> problem? Easy to fix?
> >>
> >> Thanks,
> >> TR
> >>
> > 
> > 
> > 
> > ------------------------------------
> > 
> > PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6Yahoo!
Groups Links
> > 
> > 
> >
>
Thanks a lot guys. I really appreciate your time and knowledge on this.

TR