Discussion about the Korg PolySix synthesizer

Hi, I'm trying to debug the last remaining problem in my Polysix refurb, it's regarding the LFO signal. The KLM-367 has been replaced with a Kiwisix board successfully and my local tech also did the 369 and 371 mods as indicated in the Kiwisix manual, all verified with good continuity.

Symptoms:

• If I set either MG Delay or Speed down to 0 the MG enters a fast LFO state which doesn't respond to speed knob adjustments. 
• If I set two or more of the parameters entering IC2 in KLM-369 (MG Speed, Delay, Level, PWM Speed) down to 0 it will provoke a program fault and light up all the LEDs in the front panel.
• To take it out of program fault I just need to move one or more knobs away from 0.
• To bring it out of the unusual fast modulation state I just need force Mod Wheel modulation (which is now carried through the IC2 MUX in KLM-369 too, as per Kiwisix modification).

>
> Hi, I'm trying to debug the last remaining problem in my Polysix
> refurb, it's regarding the LFO signal. The KLM-367 has been replaced
> with a Kiwisix board successfully and my local tech also did the 369
> and 371 mods as indicated in the Kiwisix manual, all verified with
> good continuity.
>
>
> Symptoms:
>
> * If I set either MG Delay or Speed down to 0 the MG enters a fast
> LFO state which doesn't respond to speed knob adjustments.
> * If I set two or more of the parameters entering IC2 in KLM-369 (MG
> Speed, Delay, Level, PWM Speed) down to 0 it will provoke a
> program fault and light up all the LEDs in the front panel.
> * To take it out of program fault I just need to move one or more
> knobs away from 0.
> * To bring it out of the unusual fast modulation state I just need
> force Mod Wheel modulation (which is now carried through the IC2
> MUX in KLM-369 too, as per Kiwisix modification).
>
> As the fault seems to be affected by many different signals it looks
> to me like a badly muxed MG signal. IC2 MUX in 369 looks suspect but
> then I don't understand why it only happens when taking values down to
> 0 and works perfect when you don't. Muxed signal travels through the
> purple ribbon cable to Kiwisix which could also be at fault. I can't
> discard the Kiwisix is doing something wrong interpreting the muxed
> data but shipping the board back to AU if the fault is somewhere else
> is overkill. Most recent boot and firmware have also been re-applied
> to Kiwisix. I haven't seen any possible points of failure in KLM-366
> as I don't think the problematic signal enters the voice board.
>
> I'd love if someone could help me out with a diagnose before taking
> any further steps. I don't have a scope to analyze the muxed analog
> data though.
>
> Thanks in advance.
>