Korg Poly 61 Freezes

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Retroman
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Korg Poly 61 Freezes

Unread post by Retroman » Sat Jun 16, 2018 4:59 pm

Hi all

As the title says i was given away a Korg Poly 61 that has issues. At firs i get no LED indications and the whole buttons and light freeze, there are also some missing keys and a - i hope small - battery leakage. I attach here a couple of photos just in case somebody can help me identify from where to start trying to fix it, i think that there maybe an issut with the power supply but please confirm if you had some previous experience on this.

Many thanks
Attachments
3.jpg
2.jpg
4.jpg
1.jpg
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Miks
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Re: Korg Poly 61 Freezes

Unread post by Miks » Sun Jun 17, 2018 10:45 am

At a first glance I can see a lot of corrosion caused by the leaking battery - see the red circles. On many of the IC pins you can see somewhat greenish colour - I think this board first needs a good careful cleaning. Some traces have to be measured to see if there's still continuity. If there are interruptions some piece of wire(s) have to be soldered to bypass the interruptions... 8O looks as if a lot of investigation & work is waiting for you 8O
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Poly61-1.jpg
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The acid from leaking batterys often 'creeps' under the ICs and causing damage(s) which cannot be seen at first glance - those can be hard to find. Desoldering 'suspect' ICs to have a look beneath them is strongly recommended - you're able to clean that area and then solder in an IC socket - which I recommend!

@ Retroman: for the service manual check your PM... :wink:
My (key related) gear (in alphabetical order):
Ferrofish: B4000+
Kawai: K1 II
Korg: M1 (up'd to EX, w/ 'Cool Blue'), M1REX (w/ 'Cool Blue'), Poly-800
Roland: D-50, D-110, D-550, PG-1000
Yamaha: AW1600, DX7IID (w/ 'Cool Blue'), EX5R, RM50, RX5, SY99 (w/ 'Cool Blue'), TG500, TX-802, YMM2
Sector101: SYEMB05 (5x), SYEMB06 (3x), EXFLM2 (1kit), MCD Sweet16 (1x), WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade
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Saul
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Re: Korg Poly 61 Freezes

Unread post by Saul » Sun Jun 17, 2018 10:53 am

Looks like quite a time consuming project you have on your hands their Retroman. The hidden damage is always going to be the biggest pain. As Miks said that leaking battery acid can get under the IC's and then you need to desolder etc. Probably not as daunting a task as on a modern synth where connections are so small it can be almost impossible to desolder some chips without damaging them.

Would be very interested to hear how you get on with it.
Saul
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Re: Korg Poly 61 Freezes

Unread post by Miks » Sun Jun 17, 2018 11:29 am

Just did a search for the battery needed: it's a 3/170DK (3.6V/170 mA).
Poly61-Battery.jpg
Poly61-Battery.jpg (16.79 KiB) Viewed 1770 times
But in this synth it has to be a NiCad type - not a NiMH! The 'charging process' for a NiMH is different! If one uses a NiMH instead a NiCad it may damage the battery... 8O
My (key related) gear (in alphabetical order):
Ferrofish: B4000+
Kawai: K1 II
Korg: M1 (up'd to EX, w/ 'Cool Blue'), M1REX (w/ 'Cool Blue'), Poly-800
Roland: D-50, D-110, D-550, PG-1000
Yamaha: AW1600, DX7IID (w/ 'Cool Blue'), EX5R, RM50, RX5, SY99 (w/ 'Cool Blue'), TG500, TX-802, YMM2
Sector101: SYEMB05 (5x), SYEMB06 (3x), EXFLM2 (1kit), MCD Sweet16 (1x), WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade
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Re: Korg Poly 61 Freezes

Unread post by Retroman » Mon Jun 18, 2018 8:06 am

Thanks always for the help. I will try it and hopefully gonna have some results soon, btw 2 questions please. How can i clean the battery leakage i mean what do i need to do it properly and second and more important please introduce me a way to use the multimeter to check continuity of the rails.

At last for the moment, is there a material that is used to repair problematic rails apart from creating "wire bridges" (have no idea about these as well i guess you connect the two working parts of a rail with a piece of wire preferably copper right ?

heard of "flux" solder but i guess this is a cleaning tool for the rails and does not repair them.

All the best, i really enjoy the process although its gonna take a while.

Miks thanks for the battery info if all goes fine i will get a new battery, 4 missing keys and knobs as well.
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Re: Korg Poly 61 Freezes

Unread post by Miks » Mon Jun 18, 2018 1:58 pm

Retroman wrote:
Mon Jun 18, 2018 8:06 am
How can i clean the battery leakage i mean what do i need to do it properly and second and more important please introduce me a way to use the multimeter to check continuity of the rails.
Here's how I would proceed:
1st: desolder all the integrated circuits which show that greenish oxidation on the pins to make sure there's no trace damage beneath!

2nd: if in any doubt check suspect traces for continuity using a meter like this:
Meter1.1.jpg
The meter should allow Diode test/continuity check - see red arrow (and user manual as well). If continuity is good you will hear a buzzing sound as long as you make contact with the trace(s). No sound - disruption. But make sure to check the 'correct' traces/connections! If one 'bypasses' a 'disruption' which isn't one (due to wrong measuring) it may blow the unit when powered on :!: :!: :!:

Then clean that area with a damped soft cloth (and/or a (not too stiff) brush) using some warm water and a mild detergent and see if that works. Thereafter clean that area using a soft cloth with some isopropylic alcohol. Allow to dry properly.

To bypass a disruption use a fine litz wire - look for solder points of components (like resistors/diodes/capacitors etc) which have connection to one of the 'halves' of the broken traces - these are good 'places' to solder the end(s) of the litz wire(s) and bypass the disruption.

3rd: solder in sockets instead of the ICs. Put back the ICs into the sockets - take care for the correct orientation (notch) of the ICs and alignment of the pins with the contacts of the socket!
I guess you connect the two working parts of a rail with a piece of wire preferably copper right?
Yes.
Heard of "flux" solder but i guess this is a cleaning tool for the rails and does not repair them.
The solder has a flux 'core' which cleans the solder joints while soldering and helps to give proper contact.
Miks thanks for the battery info if all goes fine i will get a new battery, 4 missing keys and knobs as well.
You're welcome! 8)
My (key related) gear (in alphabetical order):
Ferrofish: B4000+
Kawai: K1 II
Korg: M1 (up'd to EX, w/ 'Cool Blue'), M1REX (w/ 'Cool Blue'), Poly-800
Roland: D-50, D-110, D-550, PG-1000
Yamaha: AW1600, DX7IID (w/ 'Cool Blue'), EX5R, RM50, RX5, SY99 (w/ 'Cool Blue'), TG500, TX-802, YMM2
Sector101: SYEMB05 (5x), SYEMB06 (3x), EXFLM2 (1kit), MCD Sweet16 (1x), WaveBlade 8MB Card (1x) & 1x Programmer Unit for WaveBlade
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parametric
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Re: Korg Poly 61 Freezes

Unread post by parametric » Mon Jun 18, 2018 2:20 pm

Ha Ha ((i)) I see Miks just beat me to it . . . . :lol:
Retroman wrote:
Mon Jun 18, 2018 8:06 am
Thanks always for the help. I will try it and hopefully gonna have some results soon, btw 2 questions please. How can i clean the battery leakage i mean what do i need to do it properly and second and more important please introduce me a way to use the multimeter to check continuity of the rails.
The corrosion you see (often greenish in colour) is caused by the leaking battery contents reacting with the copper traces of the PCB. I'm not up on the chemistry involved here, but it is largely ACIDIC, and the colour would suggest copper chloride to me - cased by Hydrochloric Acid from the battery's decomposition . . .

The good news is that this is water soluble.

As it appears to have run UNDER some components, it would be best to remove those components, so cleaning can be thorough and effective . . . .

It would be BEST to remove the entire PCB from the instrument to do this operation.

desoldering ICs is arduous to be sure, but can be reasonably done using SolderWick or a solder-sucker to remove as much solder as possible - before gentle prizing with a small screwdriver - to help the IC out of it's holes . . .

If the ICs are common/cheap - it might save time to snip the legs, which can then be removed individually, much quicker.

N.B. This may not be advisable if the ICs are proprietary to the Board and therefore RARE and expensive, and possible obsolete and unobtainable . . . .

With the chips removed, then (THIS will sound HORRIBLE) - douse the corroded area with CLEAN WATER.

Let it stand for a while, then SCRUB (an old toothbrush is good for this) the area vigorously.

Rinse off and repeat - until the corrosion look to have "gone". The green deposit should be water-soluble, and should eventually be completely removable . . . .

After the final wash with water, let it dry - and give a final wash with IsoPropyl Alcohol. This will complete the drying - and will NOT affect the pcb . . . .

Check the corroded area for TRACKS that have corroded through. The breaks can be repaired with fine wire to bridge the gaps. (Cat5e ethernet cable is a good source for fine wire. The patch-cable variety are stranded though - BETTER may be the infrastructural version - which is SOLID conductor).

Tracks repaired, then its time to resolder the ICs back in. . . . arduous again :roll:

(see the comment below in the next paragraph)
Retroman wrote:
Mon Jun 18, 2018 8:06 am
At last for the moment, is there a material that is used to repair problematic rails apart from creating "wire bridges" (have no idea about these as well i guess you connect the two working parts of a rail with a piece of wire preferably copper right ?

heard of "flux" solder but i guess this is a cleaning tool for the rails and does not repair them.

All the best, i really enjoy the process although its gonna take a while.

Miks thanks for the battery info if all goes fine i will get a new battery, 4 missing keys and knobs as well.
Wire bridges, mentioned above :wink:

Solder is usually Multicore - meaning the solder contains CORES of Flux - which helps the solder to FLOW . . .

As this is an Old(er) board, you will need to use the OLD traditional Pb/Sn solder. The modern Lead-Free solder doesn't work well with EXISTING Pb/Sn solder found on these boards . . . .

IF ALL THIS SEEMS TOO MUCH . . . .

Then another approach is to try and source a "spares or repair" Korg Poly 61.

You then have a complete set of replacements for YOURS 8)

It could even turn out EASIER to repair the spares or repair board using parts from Yours?

Perhaps IT'S pcb has NOT suffered a battery leak? (IYSWIM)

Good luck - whichever you decide (Hope this has helped :wink: )

parametric
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