Discussion about the Korg PolySix synthesizer

On KLM-367 check the following:
* IC12 (TL072) pin1: must be -5V .. +5V according to PW/PWM poti
   if not, replace IC12
* IC13 (4558) pin1: must be -5V .. +5V according to PWM SPEED poti
   if not, replace IC13
* Set PWM SPEED to slowest and check IC1 (4066)/pin9: must change from
   minus to plus voltage and back (I dont know the exact values; will
   be at least -3V..+3V)
   if not, replace IC20 (LM13600) and/or IC15 (4558)
* IC1/pin6: must be +5V when WAVEFORM is at PWM position, otherwise 0V.
   if not, replace IC3 (LM339)
* IC1/pin8: must be the same as IC1/pin9 when WAVEFORM is at PWM
   position, if not replace IC1 (4066).
* TP1 (PW/PWM) near IC12: according to service manual "PW/PWM check
   and adjustment"
   if not OK, replace IC20 (LM13600) and/or IC15 (4558)

I hope this helps,

Johannes


ciscomanvann wrote:
> Nothing happens. It plays, but the width or pwm does not change. I 
> have a multimeter, how do i check this stuff out? I dont know a whole 
> lot about ICs.
> 
> --- In PolySix@yahoogroups.com, The Old Crow <oldcrow@o...> wrote:
> 
>>  First thing to do is set VCO to PW and move the width knob from 0 
> 
> to 10 
> 
>>and back to 0 and listen to see if it changes accordingly.  Then 
> 
> set it to 
> 
>>10 and change the VCO mode to PWM and move the PWM speed knob from 
> 
> 0 to 10 
> 
>>slowly and note if the cyclic modulation is audible.
>>
>>  If nothing is working then I would imagine either IC20 (LM13600) 
> 
> needs 
> 
>>replaced, or the analog switch section IC1C died and IC1 needs 
> 
> replaced, 
> 
>>or perhaps the control voltages off deMUX IC19 aren't getting there 
> 
> and 
> 
>>IC19, IC12 or IC13 is to blame (least likely though).
>>
>>  Use my schematic as it is much easier to read than the old 
> 
> service 
> 
>>manual copy.  PWM circuit is on the far right, about 2/3 of the way 
> 
> down.  
> 
>>It is marked "PWM MG":
>>
>>
> 
> http://www.oldcrows.net/~oldcrow/synth/korg/polysix/crowlm367/klm367a_
> eagle_schem.gif
> 
>>
>>  Hope this helps,
>>
>>Crow
>>/**/
>>
>>On Wed, 31 Dec 2003, ciscomanvann wrote:
>>
>>
>>>I know this sounds stupid, but how can i tell if the PWM is 
> 
> working?
> 
>>>If it is not, where do I start looking to fix it?
>>>Thanks!
> 
> 
> 
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