6 adjacent keys dead (no sound) G6,G#6,A6,A#6,B6,C7

[Altazor501]

I have a very specific dead keys issue that I’ve not been able to find a solution for, or even a lead, to what might be faulty. The piano is a Yamaha P85. The problem is that the cluster of 6 keys on the extreme right are dead. After much assessment, I concluded that the Ghl88-H board must have a fault. I replaced that board, but the problem persists. I’ve reset all of the ribbon cables all the way to the DM board without solution. I’ve thoroughly cleaned every contact point for those keys as well as the connectors. I just can’t find anything that I haven’t already addressed that explains this symptom. Any ideas on where to look, test are welcome.

I have tested the GHL88H board voltage in for the 6 keys in question and all have voltage. I also see, with my multimeter, a pulse of power going through the key(switches) for the 6 keys when they are depressed, but no sound. it is quite a mystery where to look next.

 

[happyrat1]

Check the keyboard contact board for any visible cracks.

Have you tried scoping the signal path or are you just using a multimeter?

It's probably somewhere between the key switches and the multiplexer.

Either a cold solder joint, or a failed diode, or a cracked signal trace.

Inspect again. Use magnification.

Gary

 

[happyrat1]

Try remelting the solder connections on the board. Cold solder is not always visible.