korg poly-61 not responding to pushbuttons

[crafter57]

Hi Folks, I replaced all the tact switches on the board as some were not working properly.
it worked fine for awhile but now the assigner board and programmer boards switches are unresponsive, the displays constantly shows program P5 / parameter 61 kinda strange..and won't respond to any pushbuttons. The PSU +15/-15/+5 volt rails are good. Both programmer & assigner boards have voltage, checked all transistors and diodes and are good on both.

Has anyone seen this type of problem before? I doubt both processors have gone suddenly bad
Looking at the prints, I can't seem to find whats common to both boards?

is there a re-boot sequence?
any ideas?

[sergios]

Did you change anything before it stopped working?

[garranimal]

Check the molex connectors for oxidation or breakage. Common problem with the battery corrosion issue for the Poly-61 and Polysix.

[Jabberwalky]

Mine does the reset occasionally, which I need to fix at some point. I'm almost certain there's a corroded power connector going to the cpu board. Jiggling that wire makes it reset. Could be something similar.

[crafter57]

Hi guys, yeah after posting this I did alot of searching on this problem where it just hangs on "PS-61", it looks like a bad connector or wire connection somewhere or perhaps the tape sw could be dirty. The battery was previouly changed to a coin cell and the cct board is clean around the battery area. I've been in and out of the synth since I've re-built the end-caps in real wood and tact sw replacement. I will double re-check all connections again. I was loosing my mind on this...

[crafter57]

Well after checking every strand of wire and every JST connector for continuity, they all check out good. I'm still hanging on "PS-61", to boot those darn schematics are really bad to make out. I also cleaned the slider sw in the back but even disconnecting the jack board its still the same issue.. You guys have any other ideas?

its sad how it went from functioning to crippled without knowing why
I'm trying to stay sane..

[orys]

Hey there!

Have the same problem although mine was purchased as damaged and seems to be stuck on P5-61 and won't respond to any pushbuttons.
Had battery corrosion but i managed to clean everything and have measured the CPU board which seems to work fine.
I measured all the molex connectors everywhere on all the boards and none seems to be faulty.
So what next?
Did you manage to resurrect yours?

Cheers
Tio

[crafter57]

Yes, I did resolve this issue which was a disintegrated trace due to the battery acid leakage.
Do you have a voltmeter to check continuity?

[orys]

Yes i measured continuity and it seems to have no problem.
Could it be the ROM?

[crafter57]

check continuity between pin4 of the two MCU's

[orys]

MCU's???
What are these?

[crafter57]

A microcontroller (MCU for microcontroller unit, or UC for μ-controller) is a small computer on a single integrated circuit. ... A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals.

So, IC1 and IC30 are your two MCU's

[orys]

Thanks for the info my friend.
I'll check it today and let you know!

[orys]

Hi there!

Sorry for the late reply but i was really busy at work and didn't get a chance to check the two MCUs you suggested.
I didn't quite figure out which are pins no.4 on each MCU but anyhow from left right, up down there isn't continuity except if I've made every measurement wrong.
Care to tell me which pins to measure please?

Thanks
Tio

This is the actual photo of the problematic board.

[Mooger5]

Lots of damaged traces and components on that board. You could try a thorough repair to yours, but it will take lots of time, patience, and dependant on your experience and skills.There are cloned boards for sale if you search around. The price is not inviting at first look, but it comes populated with new components.