Yamaha KX88 key group not working

[rock soderstrom]

@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!

 

[stevegkeezer]

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.

 

[rock soderstrom]

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

 

[keepitworking]

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!

 

[stevegkeezer]

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.