[Korg] [PolySix] – [Noise]
Hi,
I’m working on a Polysix which has a very noticeable white noise issue when volume is set to normal levels. I traced it back step by step but can’t figure out the cause. Here’s what was done so far:
- The noise can be modulated by the attenuator and LFO(VCA modulation) setting just like the normal audio.
- It is NOT impacted by filter, envelope, effect, waveform , key assignment settings.
- Once i disconnect the main line going from the voice to effect board, it disappears.
- went back on the voice cboard and removed components starting with filter chips, decoupling caps, op-amp and finally the last adder op amp (before connector) but the noise didn’t go away. (i was removing the set of 6 similar components together at a time, e.g all filter chips together to be 100% sure. For the op amps, all 3 wehre removed at the same time.
- When the voice-to-effect boards line is removed, i notice the ground voltage difference is about 11v on the two connectors ; however, i think one is main ground and the other is for audio. Not sure about what i should expect, i guess zero V.
- I tried to put decoupling cap between the voice and effect board but there was no difference.
- PSU voltage are perfect without any ripples or noise.
Any ideas or recommendations ?