The polysix had 1 dead voice, so we bought the replacement and changed it, that was very simple since the voices are installed in sockets, we simply had to unplug the defective one and change it.

The problem came when we decided to tune the voices.
It turns out that the first voice (the one we changed) and the second go out of tune after a few hours. We couldn't find the reason.
We have an oscilloscope and we tune the voices according to the manufacturer, and they are perfect, but the next day when we test that all this mail they have gone out of tune. ..

Any ideas?? Has anyone had the same thing happen to them and managed to find the error?

We changed some capacitors (of course with the same value) because we thought they did not give the necessary values, anyway we were testing. You don't know for sure which sector affects the tuning of the voices. ..

Maybe someone already has the answer. ..

Greetings from Argentina

I leave an image of the PCB of the voices.

 

I don't know is this have connection but...
Maybe something make battery faulty?
You checked it?

 

read this thread about the same issue, it contains some very good info: https://forum.vintagesynth.com/viewtopic.php?t=33592

It may not help you if you are on pc, but one user recommends this strobe tuner freeware for mac in the thread I have not used before: https://www.katsurashareware.com/strobetuner/ good ones can be expensive.

it looks like you just need to do the tuning and calibration correctly as per the service manual.

 

The battery saves the presets, it has nothing to do with the tuning calibration of the unit..

The Polysix is a pain to calibrate, there's a total of 17 trimmers to mess with, including the 'global' ones. You may just have some pots that are worn out and need to be replaced as well. But I wouldn't go doing that without an actual service manual..

 

I can't confirm this. I don't have Polysix. Maybe it's a bullshit but someone said:
"I just got my Polysix back from having the battery replaced, and now it's out of tune!"

If this is true for my tiny brain it looks like corelation between battery and tuning, if not directly in battery maybe somewhere between. Idk

 

This is the problem with Causation Vs Correlation. Old units like this can be very sensitive to shock, impact, shaking, the ride home in the trunk of your car, etc.

https://www.oldcrows.net/~oldcrow/synth/korg/polysix/manuals/service/miniserv.html

The service manual was linked in the thread I posted above.

 

https://9bit.se/synth-tuning/korg-polysix-tuning-the-long-story/

 

Thank you very much for the answers, the entire main board was replaced since the battery, as you said, burned part of the circuit.

We bought the board months ago at: synthronics

It works perfectly, the links are very good, especially the one on possible errors.

With my partner, you are assuming that there is a problem in the modulation section. ., we have done the tuning procedure exactly as the manual says several times but, in a few hours it fails again.

We will continue investigating

 

I saw this which mentions part failures resulting in tuning issues.

https://9bit.se/synth-tuning/korg-polysix-tuning-the-long-story/