Polysix Repair

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tomorrowstops
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Polysix Repair

Post by tomorrowstops » Mon Mar 31, 2014 7:16 pm

Hey guys!

Another day, another broken synth in the mail. This time its a Korg Polysix.

Problem: No sound, but lights up. However, all of the lights are on and pushing buttons doesn't turn them off!

This was a random ebay purchase, with little info from the seller. I assumed that the culprit was the infamous exploded battery on the klm-367 board. However, upon opening her up, I find someone has already replaced the battery! Looks like a half-assed job though; the traces look suspect. Right?

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Re: Polysix Repair

Post by rhino » Mon Mar 31, 2014 8:34 pm

Yeah. These synths are are good eye test: So many owners (and techs) take a look and say - "looks OK to me".
Pull the chips around the battery, clean the board front and back, then get a good light and a magnifying glass and Zen out for a long slow inspection.
The old battery vomit is BOTH corrosive AND conductive. Korg used some innovative - but dicey - circuits. Leakage between traces can cause nightmares. Every PolySix I have saved (5 to date) have needed 18-24 jumpers. The two I have on a shelf now are getting clone boards - got the old boards working just to prove everything else is running, but too much damage...back side of boards look like a spiderweb of jumpers.

2) look for legs eaten off chips.
3) check all vias (plated thru holes in the board)
4) more than once, the gunk has climbed up the leads of resistors and eaten them loose from the carbon inside.
5) don't trust your eyes alone. Ohm everything just in case.
When the wise man points to the stars, the fool looks at the finger.
- Confucius

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Re: Polysix Repair

Post by Dr. Phibes » Mon Mar 31, 2014 9:22 pm

Yes unfortunately those batteries seem to have been made with xenomorph blood or something similar. Absolute nightmare.

tomorrowstops
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Re: Polysix Repair

Post by tomorrowstops » Mon Mar 31, 2014 9:49 pm

YAY.

The deeper I'm digging into this board, the more damage I'm finding.

I've got an email into Scott (Old Crow's Synth Shop), probably will just cough up the $150 to save the hassle. Got the synth cheap enough anyways.

Or.....perhaps a good excuse to go with this Kiwisix jazz everyone talks about. More $$ though...

Boy, I'm 0 for 2 on fixing these damn things myself. *Sigh* maybe I'm not the hotshot electronics wiz wannabe I thought I was (gonna be)! Don't get me wrong, I can take apart anything, clean it and even get back together, but this deep electronics repair stuff is next level.

You guys are amazing, those that DIY this s**t.

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Re: Polysix Repair

Post by Dr. Phibes » Tue Apr 01, 2014 12:36 pm

Don't feel too dejected about it. Even the pros usually to concede defeat when dealing with this kind of damage. It's just a good thing that there are new replacements available.

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Re: Polysix Repair

Post by tomorrowstops » Thu Apr 03, 2014 9:46 pm

Well, I was just given a unpopulated clone pcb. Still waiting to hear back from someone who can repopulate it, or maybe I'll take it on myself. I suppose if I don't expect to get it done in an afternoon, I might be ok.

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Re: Polysix Repair

Post by radek tymecki » Thu Apr 10, 2014 9:05 am

it would be easier to fix original 367

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Re: Polysix Repair

Post by sam » Sun Apr 13, 2014 1:15 pm

having fixed over 30 poly sixes and 4 more in the workshop that's quite a bad one I see, it's a classic bad attempt of a bad fix.
The board has not been cleaned properly before fixing, you first have to clean the board with pure alcohol (toothbrush and q tips) and I would first try all the connections around ic31 and ic32.
Old crow has a handy schematic to test this.
Replace the 10mf cap near the battery.

It takes time and skill to resolder as the acid makes it all worse.

Take your time with this and check everything....one step at a time.
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tomorrowstops
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Re: Polysix Repair

Post by tomorrowstops » Sun Apr 13, 2014 4:51 pm

Yeah, I'm looking to send it in to the guy at Old Crow, but I can't see to get ahold of him...

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Re: Polysix Repair

Post by sam » Sun Apr 13, 2014 5:07 pm

What does he charge for those repairs..?
Roland Vp330 mk1.SH101.juno 6.OSCar.ARP odyssey..Tonus 2600..omni.
ms20/50. OBX.
Prophet 5
Wasp.EMS AKS.

tomorrowstops
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Re: Polysix Repair

Post by tomorrowstops » Sun Apr 13, 2014 6:31 pm

I think its $150 + shipping....

sam
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Re: Polysix Repair

Post by sam » Mon Apr 14, 2014 7:23 pm

tomorrowstops wrote:I think its $150 + shipping....
Sounds fair but some are easier than others....your board does need some love though :)

Sometimes after the repair problems can happen due to the acid in the board.
Roland Vp330 mk1.SH101.juno 6.OSCar.ARP odyssey..Tonus 2600..omni.
ms20/50. OBX.
Prophet 5
Wasp.EMS AKS.

tomorrowstops
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Re: Polysix Repair

Post by tomorrowstops » Tue Apr 15, 2014 9:44 pm

Sam - yeah, the combination of a lot of work + possible future issues led me to going with the replacement. I'm sending off for it tomorrow actually....

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Re: Polysix Repair

Post by rschnier » Thu Apr 17, 2014 1:06 am

sam wrote:Sometimes after the repair problems can happen due to the acid in the board.
Exactly, that's why I ultimately went with a clone of the PC board. Read too many accounts of further issues caused by the gook soaking into the board and then migrating to other areas of the board over time. Depends on the extent of initial leakage I suppose.
-- R.

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Re: Polysix Repair

Post by lex » Wed Oct 29, 2014 11:34 pm

I found the clone pcb (unpopulated) was very helpfull for tracing the traces to see what goes where etc.

just finished my board, I think it was about 10 jumpers needed.

only problem left is the tape in function. tape out works great, but in doesnt seem to do anything at all (even though the signal is getting to the CPU.

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