Discussion about the Korg PolySix synthesizer

After many weeks refurbishing my "new" old PolySix I am very nearly there! I have one last issue before the final tune up and I wondered if anyone had any ideas. All knobs, switches and buttons on the synth work and do what they should. The KLM-367 board is a brand new clone with new clone CPU so I assuming that it is ok.

The issue is that when I turn the PolySix on from cold, the MG frequency is properly set as designated by the preset but "leaks through" at a higher level than the preset's actual values causing a significant wobble in the tone. This happens even when changing presets. Turning the MG frequency and MG level controls to 0 will not entirely eliminate this. At the same time, the arpeggiator pulse leaks into the tone causing "catches" in the tone that can be varied by turning the Arp Speed control. However, all these issues gradually fade as the synth warms up and after a minute or two and the synth works perfectly. On switching the synth off and on again when warm there is a slight MG wobble in the tone on pressing a key which disappears in seconds. Then all is good.

This suggests to me that a component(s) is faulty and is “leaky” but starts to function correctly when it has warmed up. Any ideas?

One other thing I would like to know is whether how long the synth typically takes to initialise. I have noticed that when cold the buttons light for around 8-10 seconds before the synth initialises to preset A1, but when it is warm it initialises instantaneously.

On 2019-01-22, 00:46 cwc@dircon.co.uk [PolySix] wrote:
>
>
> After many weeks refurbishing my "new" old PolySix I am very nearly
> there! I have one last issue before the final tune up and I wondered if
> anyone had any ideas. All knobs, switches and buttons on the synth work
> and do what they should. The KLM-367 board is a brand new clone with new
> clone CPU so I assuming that it is ok.
>
>
> The issue is that when I turn the PolySix on from cold, the MG frequency
> is properly set as designated by the preset but "leaks through" at a
> higher level than the preset's actual values causing a significant
> wobble in the tone. This happens even when changing presets. Turning the
> MG frequency and MG level controls to 0 will not entirely eliminate
> this. At the same time, the arpeggiator pulse leaks into the tone
> causing "catches" in the tone that can be varied by turning the Arp
> Speed control. However, all these issues gradually fade as the synth
> warms up and after a minute or two and the synth works perfectly. On
> switching the synth off and on again when warm there is a slight MG
> wobble in the tone on pressing a key which disappears in seconds. Then
> all is good.
>
>
> This suggests to me that a component(s) is faulty and is “leaky” but
> starts to function correctly when it has warmed up. Any ideas?
>
>
> One other thing I would like to know is whether how long the synth
> typically takes to initialise. I have noticed that when cold the buttons
> light for around 8-10 seconds before the synth initialises to preset A1,
> but when it is warm it initialises instantaneously.
>
>
>
>

You may have a failing 10uf cap on one of your other boards, pulling the supply down on startup(?). I had a Poly61 and a CX3 with leaky shorted 10uf caps, easy to spot as they will corrode around the solder pad. (Replaced all of them on the CX3)

I would check the programmer board if the 367 is all new. Hope this helps...

On January 27, 2019 at 3:26 PM "cwc@dircon.co.uk [PolySix]" <PolySix@yahoogroups.com> wrote:

 

 

HI Johannes, Thanks for your response. I have replaced all the electrolytic capacitors on the power supply including the two large 4700uf and 2200uf ones. Voltages are adjusted and spot on. Since my original post I have noticed that if I disconnect the harness from CN05 from the clone KLM367  (i.e. the connector comes from the patch select, write enable/disable and tape enable/disable part of the KLM371 Programmer Board), patch A.1 comes up without the problematic modulation when I turn the synth on.