Vintage Synth Repair

I recently received a dead Korg PolySix. The battery was replaced and the damaged traces were cut out and replaced with 30AWG wire. Currently when the synth turns on, the LEDs briefly light up and then go dark except for Program 1 and Bank 1. As they should.

There is no sound, however. Only hiss. When I turn up the volume pot, the hiss gets louder.

The voltages all match the schematic.

I suspect something is awry on the KLM-366 board.

Any tips on where to look first?

what happens when you enter Manual mode?

On Aug 26, 2009, at 12:32 PM, imbuedblue wrote:

> I recently received a dead Korg PolySix. The battery was replaced  
> and the damaged traces were cut out and replaced with 30AWG wire.  
> Currently when the synth turns on, the LEDs briefly light up and  
> then go dark except for Program 1 and Bank 1. As they should.
>
> There is no sound, however. Only hiss. When I turn up the volume  
> pot, the hiss gets louder.
>
> The voltages all match the schematic.
>
> I suspect something is awry on the KLM-366 board.
>
> Any tips on where to look first?
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>

OK, here we go.

First we determine if the key assigner routine works (read: if the voices
are "driven" at all).
If you look at the KLM-366 you'll probably be able to identify the voices.
Each voice has a small activity LED close to the trimmers. Do those LED's
light up with key presses?
If so we move on further: Test Point 1 (TP1) on the KLM-366 is the Signal
output. Connect a 'scope to it and see if something is visible if you play
notes on the keyboard.


(All of this of course assumes that you have dialed in a sound that
actually outputs some noise. Best use the sawtooth wave, put cutoff to 10
and resonance to 0 and switch the Amp into "gate" mode).

There is also a Polysix yahoogroup that has a wealth of information on
fixing those machines.


-- 
Malte Rogacki

Thanks Malte. No, the activity LEDs do not light when keys are pressed. So its a key assigner problem or perhaps a problem with the keyboard contacts.