Korg Polysix - resonance doesn't work + other issues

Pulling out your hair? Don't know what to do or where to go? Ask in here.
Forum rules
READ: VSE Board-Wide Rules and Guidelines

If your Help request has been solved, please edit your first post in order to select the Image Topic Icon to let others know your topic has been solved.
Post Reply
andreasledet
Newbie
Newbie
Posts: 7
Joined: Thu Jan 21, 2016 9:14 pm

Korg Polysix - resonance doesn't work + other issues

Post by andreasledet » Fri Jul 08, 2016 12:51 pm

Hi everyone.

After not having used my trusty old Polysix for a month or so, I turned it on yesterday to have some fun with it.

However, I immediately noticed that it didn't sound like it used to.

First off, it was slightly out of tune between octaves. This seemed to correct itself after having the synth on for quite some time, but is still noticeable on some presets.

Secondly, (and freaking me out the most) the resonance and attenuation knobs doesn't do what I want them to!

On some presets, the resonance knob has some effect, but not like it used to. On most presets, it just works as a reverse volume knob - when I turn the resonance knob clockwise, the volume goes down. Regardless of the cutoff setting.

The attenuation knob seems to work OK for most presets, but I noticed that one of my presets was quite low in volume, and turning up the attenuator actually seemed to lower the volume even more.

I have absolutely no clue what could be causing this. I know a fair bit about electronics, and I have worked a little bit on the Polysix before, but I just don't know what to look for to address these problems. :|

Any help would be greatly appreciated!

Thank you in advance.

User avatar
sneakthief
Newbie
Newbie
Posts: 78
Joined: Fri Jun 02, 2006 9:43 am
Location: Berlin
Contact:

Re: Korg Polysix - resonance doesn't work + other issues

Post by sneakthief » Fri Jul 08, 2016 5:22 pm

Even if you've already replaced the battery, minor or even invisible battery leakage can start a cancerous chain reaction on traces on the cpu board. Everything you mention hints at chaos in that section. Can you post a pic of the cpu board is and around the battery location?
sneak-thief: raw electrofunk!
http://sneak-thief.com

andreasledet
Newbie
Newbie
Posts: 7
Joined: Thu Jan 21, 2016 9:14 pm

Re: Korg Polysix - resonance doesn't work + other issues

Post by andreasledet » Sat Jul 09, 2016 7:21 am

The battery was replaced by a former owner.

I opened it up and had a look. There are some areas around the battery that shows signs of a leak, but they've been like that since I got the synthesizer - the damage was caused by a leak years back before the former owner replaced the battery.

Image

The battery itself looks to be in good nick.

Image
Image

I had a look around the other parts of the machine, but can't see anything out of order with my bare, unexperienced eye. I attached pictures, hoping that some of you might be able to spot something.

Image
Image
Image
Image
Image
Image

I still don't have any idea what the problem might be. Anyone?

andreasledet
Newbie
Newbie
Posts: 7
Joined: Thu Jan 21, 2016 9:14 pm

Re: Korg Polysix - resonance doesn't work + other issues

Post by andreasledet » Sat Jul 09, 2016 7:43 am

Also - after having the battery out and loading my presets back in, there are even more volume difference issues. About half of the presets are very low in volume, whereas the others are normal. Still same issues with tuning and resonance.

User avatar
Jabberwalky
Synth Explorer
Synth Explorer
Posts: 2161
Joined: Fri Apr 01, 2005 6:03 pm
Gear: A hybrid of vintage and modern junk
Band: Variar
Location: Pgh, PA
Contact:

Re: Korg Polysix - resonance doesn't work + other issues

Post by Jabberwalky » Sat Jul 09, 2016 12:47 pm

We would probably need mega close up, well lit pics around the battery. Corrosion can continue happening long after the battery was replaced. You could check for continuity in that area. Read over this thread too. http://electro-music.com/forum/topic-37208.html

Although it appears you have the leak damage, you're certainly not alone with that and there is tons of info online about it.

andreasledet
Newbie
Newbie
Posts: 7
Joined: Thu Jan 21, 2016 9:14 pm

Re: Korg Polysix - resonance doesn't work + other issues

Post by andreasledet » Sun Jul 10, 2016 11:03 pm

Took some new pics:

Image

Image

Image

Image

User avatar
sneakthief
Newbie
Newbie
Posts: 78
Joined: Fri Jun 02, 2006 9:43 am
Location: Berlin
Contact:

Re: Korg Polysix - resonance doesn't work + other issues

Post by sneakthief » Mon Jul 11, 2016 10:13 am

Those traces around the battery are looking like Swiss cheese. Also, who knows what's happening under the chips in that area.

You can see that the 74HC08 next to the battery was removed and a socket was put in.

If you're handy with a multimeter you could start testing all suspect traces for continuity and use wires to jumper any broken ones.

The only other options involve buying a new CPU pcb and swapping all the parts or buying the Kiwi upgrade:

https://sites.google.com/site/jedjorgensen/

http://kiwitechnics.com/kiwisix.htm

Sending it to a tech will only delay the inevitable decay.
sneak-thief: raw electrofunk!
http://sneak-thief.com

andreasledet
Newbie
Newbie
Posts: 7
Joined: Thu Jan 21, 2016 9:14 pm

Re: Korg Polysix - resonance doesn't work + other issues

Post by andreasledet » Mon Jul 11, 2016 2:26 pm

I'm looking at a replacement KLM367A board on eBay for 149 euros.
Thinking of just ordering it, but how certain is it that my problems are caused by this board? It's quite a bit of money for me right now if it doesn't solve the problems.

It sounded on the previous owner like the battery had been replaced several years ago - will a leakage that old still cause new issues like the ones described in the OP?

User avatar
Jabberwalky
Synth Explorer
Synth Explorer
Posts: 2161
Joined: Fri Apr 01, 2005 6:03 pm
Gear: A hybrid of vintage and modern junk
Band: Variar
Location: Pgh, PA
Contact:

Re: Korg Polysix - resonance doesn't work + other issues

Post by Jabberwalky » Mon Jul 11, 2016 8:08 pm

Image

Continuity check. It looks it will be an uphill battle on this one. Perhaps the battery was replaced, but the damage was already done, and moisture keeps it going forever.

Post Reply