Korg M1 buttons not working

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Mooger5
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Re: Korg M1 buttons not working

Post by Mooger5 » Thu May 02, 2019 9:41 pm

Just post photos of the actual unit. For what you're intending to do, you'd have to open it up anyway.
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mikepctvman
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Re: Korg M1 buttons not working

Post by mikepctvman » Fri May 03, 2019 3:13 am

Ok im going to work on it again tomorrow or over the weekend. I had a chance to fiddle with it again for a bit today and i jumped a wire from CN4B pin 3, to the third wire of connector CN5A on the mainboard and (strangely) the up/down buttons started working but would scroll through the settings out of order, but i may be onto something finally. Pics to come next...

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Re: Korg M1 buttons not working

Post by Rasputin » Fri May 03, 2019 12:25 pm

mikepctvman wrote:
Fri May 03, 2019 3:13 am
I jumped a wire from CN4B pin 3, to the third wire of connector CN5A on the mainboard and (strangely) the up/down buttons started working but would scroll through the settings out of order
I'm assuming that was a typo and you mean CN4B on the mainboard side.

But this should not be necessary if you can measure continuity between those two points already. If jumping a wire produced those new results then something went awry during your initial continuity tests. There would have to have been a section with no continuity that you either skipped over, misinterpreted, *or* your testing temporarily restored continuity which promptly failed again during power-up. The last option does occur occasionally as the pressure/motion from the probes or the physical positioning of the boards/ribbons (board flex, broken wire strands) can sometimes make or break an intermittent connection.

As such, the alternate method to what you tried is to jump the button panel from the point of SW9 (side of SW9 *without* the diode attached) to the mainboard at the point of IC25 pin 13. Doing it this way will "cut out the middle-man", so to speak.

Did the other malfunctioning buttons aside from up/down also starting working to some degree?
Last edited by Rasputin on Fri May 03, 2019 7:19 pm, edited 1 time in total.

mikepctvman
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Re: Korg M1 buttons not working

Post by mikepctvman » Fri May 03, 2019 4:09 pm

If I recall it was CN5A, but regaurdless it still didn't function properly, and the A-B-C-D buttons still did not work. Should I try a jumper from the third pin of CN4B to IC25 pin 13 (like in the photo drawing below) or do those diodes need to be in the trace?
Attachments
km1.jpg

Rasputin
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Re: Korg M1 buttons not working

Post by Rasputin » Fri May 03, 2019 8:26 pm

mikepctvman wrote:
Fri May 03, 2019 4:09 pm
Should I try a jumper from the third pin of CN4B to IC25 pin 13 (like in the photo drawing below)
That's the right idea, but this picture might make the situation clearer. The purple area is the commonality between the buttons that aren't working. The red wire is a signal which usually passes from the mainboard to the button board over the CN4 connector, and is the signal which supplies the purple area. If IC25 pin 13 doesn't work, or CN4 cannot carry that signal then the purple area goes dead. Similarly, if there is a break (bad trace?) between CN4B pin 3 and the first button in the purple area (SW9) then all the buttons in the purple area will die.

Any of these situations matches your symptoms.

Image

Taking the signal directly from IC25 pin 13 and jumping it to any of the yellow star points should energize the purple area. Connecting it to the purple side of SW14 is shown in the picture, but it doesn't really matter so long as it's one of the star points representing where the dead buttons are touching the purple area.

The other side of each of the buttons goes to a separate line (one per button, each with a diode), and is not the side you want.

You'll notice that the trace between SW9 and CN4B pin 3 is thinner than the majority of the purple area, so if trace damage is causing this problem, that would be a key place to look.

Since all six buttons in that group are not working then we can safely say that the problem lies somewhere at or between SW9 and IC25 pin 13. Jumping those two points directly (or as shown in my picture) cuts out the middle-man by connecting the purple area directly to IC25.

As a slight digression: If the up and down buttons were working but the A, B C, D (SW11, 12, 13, & 14) buttons were not then the purple trace area between SW10 and SW11 would be suspect. It couldn't be CN4 or IC25 because that would knock out SW9 and SW10.

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Re: Korg M1 buttons not working

Post by mikepctvman » Fri May 03, 2019 11:57 pm

Well I’m happy to say that way worked! All buttons function as they should, I know it’s not the proper fix but it works for me. I soldered the jumper wire to the exact points in your illustration, thank you so much for your input Rasputin & mooger I don’t think I would have found this info anywhere else :D

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Re: Korg M1 buttons not working

Post by Rasputin » Sat May 04, 2019 12:15 am

mikepctvman wrote:
Fri May 03, 2019 11:57 pm
Well I’m happy to say that way worked! All buttons function as they should, I know it’s not the proper fix but it works for me. I soldered the jumper wire to the exact points in your illustration, thank you so much for your input Rasputin & mooger I don’t think I would have found this info anywhere else :D
Terrific!

:D

Successes and appreciation like this remind me why I keep coming back here despite the occasional sense of entitlement and ingratitude. You're very welcome, but I have to thank you as well :)

Mooger5
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Re: Korg M1 buttons not working

Post by Mooger5 » Sat May 04, 2019 4:05 pm

:thumbleft:
I'd personally keep on trying to restore the synth to its original condition but hey it's fixed, so I'm happy it's working for you.
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