E piano keyboard defective, one block of 18 keys does not work.

[rock soderstrom]

Hi guys, as described I have an old Korg EC100H E Piano here with a defective keyboard.

Damage caused by an unknown drink, the fault is clearly on one of the keyboard PCBs. I have removed everything and cleaned all contacts, unfortunately no function.

I have the suspicion that a trace on the PCB was killed by the drink.

18 keys are mute, in a block from C5 to F7.

Anyone have a clever idea how I can best fix this? How does such a diode matrix work again, I thought they were organized in blocks of 8?

 

[JohnRoberts]

you probably need to take it further apart... yes, could be multiplexed in banks of 8 or not.

JR

 

[rock soderstrom]

you probably need to take it further apart...

I had already completely disassembled this POS, quite time consuming. I'll have to do it again, that's already clear to me. I thought I'd get some advice here beforehand, so that it stays with one another operation.

 

[abbey road d enfer]

Have you checked all the diodes on the PCB? It takes one duff to inhibit a whole set of keys.

 

[rock soderstrom]

Have you checked all the diodes on the PCB? It takes one duff to inhibit a whole set of keys.

Thats my next step tomorrow morning.

I should have done this right away, but I was sure I could solve it with a cleaning job since the PCB was so soaked with this sticky drink.

 

[rock soderstrom]

Thats my next step tomorrow morning.

Diodes are all okay.

View attachment 20220608_094932_001.mp4

As you can see, the drink has corroded the traces on the PCB and the solder joints. Despite thorough cleaning, I can not get rid of the corrosion. Now its resolder time..

The contacts under the rubber thingy are all cleaned and ok.

 

[beatnik]

Perhaps it's worth contacting Fatar and ask if they can provide a replacement pcb.
It looks like the damaged area is quite large and I would be worried even if you manage to fix it, it won't be reliable on the long term

 

[rock soderstrom]

Perhaps it's worth contacting Fatar and ask if they can provide a replacement pcb.
It looks like the damaged area is quite large and I would be worried even if you manage to fix it, it won't be reliable on the long term

The piano is quite old, rather unlikely that there are still individual boards from Fatar avaible.

I think you're right, the PCB is probably f*cked. I can't get it to work anymore. Very frustrating...

 

[magic]

I had exactly this problem on a keyboard in for repair a little while back , although I have to say it was not as bad as yours. Quite simply I reckon you have some tracks corroded that are now O/C. Go around with a multimeter on "bleep" and test between pads. You may well find that it is only a couple that have actually broken. The break is likely to be adjacent to the solder pad. Firstly carefully scrape and expose the track next to the pad at each end and then run solder along the track . If it is still O/C solder a piece of connecting wire between the pads. I use wire wrap wire and a dab of glue. It is delicate work and needs a steady hand. However you might just surprise yourself and fix it quite quickly. Slight concern when you say you cleaned the rubber switches.. Just make sure they are still working as a switch... Good luck.

 

[rock soderstrom]

I had exactly this problem on a keyboard in for repair a little while back , although I have to say it was not as bad as yours. Quite simply I reckon you have some tracks corroded that are now O/C. Go around with a multimeter on "bleep" and test between pads. You may well find that it is only a couple that have actually broken. The break is likely to be adjacent to the solder pad. Firstly carefully scrape and expose the track next to the pad at each end and then run solder along the track . If it is still O/C solder a piece of connecting wire between the pads. I use wire wrap wire and a dab of glue. It is delicate work and needs a steady hand. However you might just surprise yourself and fix it quite quickly. Slight concern when you say you cleaned the rubber switches.. Just make sure they are still working as a switch... Good luck.

Thanks for info! That's roughly the way I tried it, unfortunately the result was not stable enough. Due to the key action, mechanical force presses on the PCB what leads again to contact breakage.

I never thought that only one drink can have such fatal effects.

The solution was to replace the PCB. I was incredibly lucky, I was able to find an identical, defective piano here in my area!

After explaining to the owner what I was up to and that it was for a youth rehearsal room, I got the piano for free!