Yamaha KX88 key group not working

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@rock soderstrom I didn't see any corrosion on the ribbon cable, cleaned all the pins and sprayed the connector with contact cleaner. I also did a bunch of wiggling of the ribbon cable to try to reproduce it but nothing.

The only time I thought I had the issue pinned down is when I cleaned the PCB which is what seemed to fix it the first time. I wasn't sure if it was due to cleaning it or hitting the diodes a bit that made it start working again. I've also gone through and individually wobbled the diodes as well.

I do see some areas on the board that look like partially cold solder or possibly corrosion.
Okay, I see. Sometimes such errors are really hard to find without a good strategy and can be quite annoying. I think that signal tracing gives the best chance to find the problem. A bad solder joint or a trace with a hairline crack on the PCB can be barely visible. Check where you lose the signal is the best advice I can give you.

Again, good luck! (y)
 
I checked for continuity on all the traces on the keyboard and for the most part everything looked good.

I did noticed some spots where the ohms were registering significantly less. It took that as that I possibly had some contact corrosion or a cold solder. So I touched up every joint on the board for good measure. So far everything been working great. Not going to say it's fixed yet, I will update the thread it in a couple weeks.

Don't want to jinx it. :)
 
I checked for continuity on all the traces on the keyboard and for the most part everything looked good.

I did noticed some spots where the ohms were registering significantly less. It took that as that I possibly had some contact corrosion or a cold solder. So I touched up every joint on the board for good measure. So far everything been working great. Not going to say it's fixed yet, I will update the thread it in a couple weeks.

Don't want to jinx it. :)
I hope the best that it remains stable and the bad ghosts do not come back again 👍
 
I joined today to share my experience with repairing a similar problem.

In my case I had 3 missing D notes on the upper half of the keyboard. Opening up the beast and doing the typical cable and contact checks yielded a clue where when I pressed down on one of the keyboard circuit boards (upper one), the problem would come and go and sometimes even seem to be fixed. Closer examination with a magnifier showed 3 or 4 solder connections that had failed probably due to mechanical stress. Re-soldering those pins fixed the issue. In addition I also had my mode stuck in dual mode. Per the manual, the default mode buttons are the MS 1-3 buttons. They seemed non-responsive until I reinserted all the ribbon cables and reset the system. I'm not sure how key the reset was, but I can now toggle modes--although it does appear the LED's are non-functional on those MS buttons.

Hope that helps someone some day!
 
Glad you were able to resolve your issue. The keyboard has been working great for me that last couple months without issue since touching up the solder points.
 
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