Discussion about the Korg PolySix synthesizer

Hi Stuart,

I had the same problem as you recently, i guess. Sounds pretty 
similar. And i found the solution: it was a trace next to the battery 
that was little corroded (black spots) by acid from a leaking battery 
in the past. The battery i removed already 1,5 year ago and cleaned 
everything, but under the surface the corrosionprocess can still go 
on, i discovered. The PCB around the battery is slightly less
glancing and the silver of the via's is not that shiny (because of
the 
leaking). In that area i measured the resistance with an ohmmeter of 
every trace and found out 1 partly bad trace, just under IC 31. 

It was the trace from leg 35 of IC 21 to a via (under the text
4.GNDA) just in front of the ground-leg of the battery (closest to
the edge of the board, not the ground-trace). (It crosses the legs of
R17, but doesn't touch them)(crosses also between the legs 3 and 4 of 
IC31 and 12 and 13 of IC31, but doesnt touch either) I made a bypass 
from leg 35 to the via under GNDA and it all solved my problems!

I wouldn't have been able to solve the problem without all the 
information Old Crow gives us on his great site:
http://www.oldcrows.net/~oldcrow/synth/korg/polysix/index.html
Thanx Crow!

Problem description:
My Poly6 gives "at random" behaviour lately. 

When i got the synth 1.5 years ago i was aware of the fact that the 
battery could be a problem. I opened the synth and it had leaked a 
little bit, but it was not white crumbled stuff as on the pics of Old 
Crow. You could nearly see that the NiCad had leaked. Only a little 
bit "oily" around IC 31, IC32 and R17, as far as i can see. And the 
vias around IC31 are not that silver-shiny as all the others on the 
board.

I took away the NiCad battery and replaced it with a Lithium exactly 
as Old Crow tells us on his site.
Some legs of the IC31 were blackened, it was as if there was a thin
black paint on the legs. But it was not fixed to the metal and i was
able to scratch it away carefully with a screwdriver. All the legs are
cleaned in a dry way. Everyhing is clear and silver-color.
The visible "oil" il cleaned with some alcohol wetted q-tips.

the synth worked perfect as i got it, and also after the batterymod.
Now, a year after the repair, the synth starts doing strange:
*It starts mostly when the synth is on for 10 seconds, and stays for 5
or ten minutes, then dissappears. It can come back at random also.
*The sound is in this situiation not clear but noisy. It is as if you
hear the chords i play PLUS a permanent noisy C-Sound. It is like it 
is distorted. It is like there is modulation by a LFO very high 
frequent, but is much more dirty.
* sometimes the frequency of this signal varies and can go "Puh Puh 
Puh Puh" in an unregular way. Its like its triggered in an slower or 
faster but unregular way
*it has nothing to do with the KLM 366 because its undependant of 
which voice is playing.
*when the problem is seriously, one or more of the following knobs 
don't respond anymore: octave, waveform, PW/PWM and PWM-speed. 
Sometimes also the MOD selector (vco/vcf/vca) doesn't respond either. 
The problem is never with the VCF, VCA, Arpeggiator, or effect 
section.
* it is like a "walking" virus. The one day it only in the PWM-section
most of the time); all sounds based on saw are perfect, those based on
PWM are "noisy". The other day its only in the sounds with saw, put on
16. On 8' it seems gone. Next day its located in the SUB-oscilator. No
problem with 1 octave down or two octave down but off gives the noise
again. Once the ADSR pots did strange when i turned them they said 
tick,tick, tick in an unregular way when i turned them slowly like 
there were given triggers at random.
* the effect is not permanent. It mostly dissappears after 10 minutes 
or so. But it can return suddenly also! Yesterday (july 2002) the 
noise stayed and i let the synth on for 3 hours. When i returned and 
tried to play it there was no sound at all. it was like the keyboard 
was dead! After "cooling down" (synth off for 20 minutes) there was 
normal sound again, only with the noise.
* it is returning more and more (half a yeau ago at first) after that
* now its almost permnently there.

I hope i can help those P6-owners who have these "noise-problems also 
by giving the solution i found. Good luck!

Defros
Holland







--- In PolySix@y..., "Sime, Stuart" <stuart.sime@n...> wrote:
> hi everyone.  i've been a polysix owner for exactly one day!
>  
> there is one prob...i can't seem to get rid of a constant 'white 
noise' type
> sound coming out of either output.  i'm pretty sure its nothing to 
do with
> any of the parameters i've set.
>  
> can someone please help??
>  
> cheers.
> 
> 
> 
> 
> 
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