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!