Discussion about the Korg PolySix synthesizer

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!