Good evening, best regards for 2025 to everyone in this group.
I have acquired a Yamaha PSR-GX76 with a few dead keys ; D4 ,D5 , D6 ,
G#5 , G#6.I have started troubleshooting the keyboard by cleaning the circuit board and contact strip but these keys remain unresponsive.
I have done some preliminary checks that has taken me to the second circuit
board ( M/J ) and this houses the CPU. I have down loaded the service manual and trying to walk through it and for worse case scenario, I have already checked in with Yahmaha on availability of this IC or the M/J circuit
board after scowering the internet and neither had parts available.
I am unable to locate a data sheet for XY512A00 which is the CPU to confirm my measurements,I want to be sure if this IC has become faulty.I have attached my findings after testing the IC.

 

Good evening, best regards for 2025 to everyone in this group.
I have acquired a Yamaha PSR-GX76 with a few dead keys ; D4 ,D5 , D6 ,
G#5 , G#6.I have started troubleshooting the keyboard by cleaning the circuit board and contact strip but these keys remain unresponsive.
I have done some preliminary checks that has taken me to the second circuit
board ( M/J ) and this houses the CPU. I have down loaded the service manual and trying to walk through it and for worse case scenario, I have already checked in with Yahmaha on availability of this IC or the M/J circuit
board after scowering the internet and neither had parts available.
I am unable to locate a data sheet for XY512A00 which is the CPU to confirm my measurements,I want to be sure if this IC has become faulty.I have attached my findings after testing the IC.

Good evening, best regards for 2025 to everyone in this group.
I have acquired a Yamaha PSR-GX76 with a few dead keys ; D4 ,D5 , D6 ,
G#5 , G#6.I have started troubleshooting the keyboard by cleaning the circuit board and contact strip but these keys remain unresponsive.
I have done some preliminary checks that has taken me to the second circuit
board ( M/J ) and this houses the CPU. I have down loaded the service manual and trying to walk through it and for worse case scenario, I have already checked in with Yahmaha on availability of this IC or the M/J circuit
board after scowering the internet and neither had parts available.
I am unable to locate a data sheet for XY512A00 which is the CPU to confirm my measurements,I want to be sure if this IC has become faulty.I have attached my findings after testing the IC.

I would like to report my success today, on Monday I took a deaper dive into my PSR-GX76 has someone had pointed me to the matrix from another forum.
Monday, armed with my multimeter ,hook lead ,alligator lead ,sewing needle, magnifying glass, a markerand my laptop I once more opened PSR-GX76 with a mission to find a broken trace has Midnightvisions / Trev suggested ( the Matrix ).
After a closer examination of the schematic, I had realized that all five dead keys shared traces 3 and 4 in the matrix which sends signal from circuit board MK 76H to circuit board M/J via 12 lead cable ( in this case leads N12 and N 22 ) which connect both boards.
Continuity testing from disconnected cable wire N12 along trace 3 of the matrix at all relating contacts were execellent for all 5 keys. Switching to N22 and testing along trace 4 of the matrix contacts revealed that this is where I would find the broken trace.
Adding my needle as a probe to my alligator clip tightly with magnifying glass I found the broken trace a few milimeter after the second contact after N22 enters Mk 76 H.
I tried soldering with flux after creating contact point with needle, but too tedious, so I connected with a wire to the first dead key D4.Thanks for allowing me to post in the forum this might help someone else. Below photo where I found the broken trace :

Photo below is my bypass repair :

I really hope this might help someone.