Synth-DIY Yahoo! Groups Archives

Thread

tuning issue still... / local repair STL

2015-07-23 by Jack Lane

Hi All,

I am REALLY wanting to get my P6 up and running properly but it's not quite there. Any input will be greatly appreciated! I am not opposed to bringing it to a local shop and having it fixed. In fact, I have already... to 2 different shops but neither of them could fix the tuning issue. I am in St. Louis, MO, USA and if anybody on this forum can point me to somebody in St. Louis that is a known authority for troubleshooting and fixing this beautiful beast, then please do. I have already posted this same basic message on my local craigslist but have not gotten any replies... By the way, I am not opposed to buying a KIWI board and power supply if I would be absolutely positive it would fix everything but I have already spent so much time and money on this already. I would hate to drop another $500 plus and have it still be unplayable.....

Brief recap of service already performed:

Repair shop 1) It had the dreaded battery leaking issue – I had the new proper battery installed and all of the corroded traces redone, tested and (supposedly) fixed -- very labor intensive repair)...

Repair Shop 2) All suspect parts (capacitors, resistors, and 1 voice chip) have been replaced and even after full recalibration per service manual, (including tuning recalibration) the tuning problem remains....

1) It does not tune up properly -- for ex. you can get middle C spot on but then the next C sounds more like an E flat etc..... and on a seemingly related note....

2) All of the patches -- including most settings in manual mode have this drone like pitch dropping thing going on as if the pitch wheel is always turning down slowly dropping in pitch when most notes are sustained.

The Sci Fi sounds this machine makes are absolutely incredible but.... I want to ALSO use it a regularly tuned playable musical instrument... Anybody??? PLEASE AND THANKS !!!!!!!!!

Re: tuning issue still... / local repair STL

2015-07-23 by swamp.gigs@googlemail.com

Hi, The issue with the tuning is most likely the optocoupler - see Stefan Huebner's excellent blog on this, which also shows how to diagnose it... http://huebnerie.de/blog/?p=318

The part is readily available from Australia (it resides on the KLM366 voice board.) - http://www.ebay.co.uk/itm/HTV-4E-P1501-REPLACEMENT-PART-OPTOCOUPLER-HTV-P-1501-KORG-POLYSIX-PHOTOCOUPLER-/321638416753?pt=LH_DefaultDomain_15&hash=item4ae324c171

As for the drone gliss issue - this sounds like the 367 battery board hasn't been fully sorted... I had something similar, and if I recall correctly, it was down acid damage under the cpu... not that it's necessarily the same for your board...

Regards - Tony

Re: tuning issue still... / local repair STL

2015-07-24 by jacklane@sbcglobal.net

Thanks Tony! Unfortunately the octocoupler has already been replaced. So we can rule that out. Both sides of the board have been thoroughly cleaned and all the traces redone everywhere that the battery acid leak occurred. I am open to other thoughts / suggestions you or anyone may have. I am even half tempted to by a kiwi six replacement board and power supply If could be sure it would fix these issues but would hate to drop that kind of money and still not have the P6 fixed.... Jack

Re: [PolySix] Re: tuning issue still... / local repair STL

2015-07-24 by Bob Grieb

Hi,

On the PolySix, the DAC output is linear. Every step is a semi-tone. That voltage is
converted into an exponential one for the oscillators by the anti-log circuit. (which includes
the opto-coupler of course)

If all of the oscillators show the same poor tuning, then the problem is in the anti-log
circuit, or in the S&H (4051) at its output.

I uploaded a procedure a while back to the files section for adjusting the anti-log
trimmers. You could also use that to help measure whether the anti-log is working
correctly with just a voltmeter. If the trimmers have been messed with, then you will
definitely need to re-calibrate it.

Also I uploaded a re-drawn schem of that circuit so you can see a little better how
it works.

Bob Grieb

--------------------------------------------

On Fri, 7/24/15, jacklane@sbcglobal.net [PolySix] <PolySix@yahoogroups.com> wrote:

Subject: [PolySix] Re: tuning issue still... / local repair STL
To: PolySix@yahoogroups.com
Date: Friday, July 24, 2015, 9:57 AM

Thanks Tony! Unfortunately the octocoupler has
already been replaced. So we can rule that out. Both sides
of the board have been thoroughly cleaned and all the
traces redone everywhere that the battery acid leak
occurred. I am open to other thoughts / suggestions you or
anyone may have. I am even half tempted to by a kiwi six
replacement board and power supply If could be sure it would
fix these issues but would hate to drop that kind of money
and still not have the P6 fixed.... Jack

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Re: [PolySix] Re: tuning issue still... / local repair STL

2015-07-24 by Johannes

It might be one of the 4069 buffers that feed the R2R DA converter
(IC6, IC7)
Or, I had this once, the MPX CV signal (before the antilog) is routed
all over the PCB. There was some minor battery acid damage even on the
KLM-366 which affected the long PCB trace. You might cut it on both ends
and route a wire directly.

Johannes

Am 2015-07-24 um 17:07 schrieb Bob Grieb bobgrieb@yahoo.com [PolySix]:

> Hi,
>
> On the PolySix, the DAC output is linear. Every step is a semi-tone. That voltage is
> converted into an exponential one for the oscillators by the anti-log circuit. (which includes
> the opto-coupler of course)
>
> If all of the oscillators show the same poor tuning, then the problem is in the anti-log
> circuit, or in the S&H (4051) at its output.
>
> I uploaded a procedure a while back to the files section for adjusting the anti-log
> trimmers. You could also use that to help measure whether the anti-log is working
> correctly with just a voltmeter. If the trimmers have been messed with, then you will
> definitely need to re-calibrate it.
>
> Also I uploaded a re-drawn schem of that circuit so you can see a little better how
> it works.
>
> Bob Grieb
>
>
> --------------------------------------------
> On Fri, 7/24/15, jacklane@sbcglobal.net [PolySix] <PolySix@yahoogroups.com> wrote:
>
> Subject: [PolySix] Re: tuning issue still... / local repair STL
> To: PolySix@yahoogroups.com
> Date: Friday, July 24, 2015, 9:57 AM
>
>
>
>
> Thanks Tony! Unfortunately the octocoupler has
> already been replaced. So we can rule that out. Both sides
> of the board have been thoroughly cleaned and all the
> traces redone everywhere that the battery acid leak
> occurred. I am open to other thoughts / suggestions you or
> anyone may have. I am even half tempted to by a kiwi six
> replacement board and power supply If could be sure it would
> fix these issues but would hate to drop that kind of money
> and still not have the P6 fixed.... Jack
>
>
>
>
>
>
>
>
>
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>
>
> ------------------------------------
> Posted by: Bob Grieb <bobgrieb@yahoo.com>
> ------------------------------------
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>
>
>
>

Re: tuning issue still... / local repair STL

2015-07-29 by fonik@web.de

Hi Bob,

As a side note, i am in the process of checking and re-capping the AntiLog circuitry of the polysix i have on my bench. Fun fact is that the values of the RC network R95-C22 are quite different than from korg schematics. 220k-100uF iso 330k-47uF, however, the resulting f is the same ;-P

Maybe they just used caps they had on hand.

Cheers,

Matthias