F4 to B4 keys are out of tune

Some issues with my Yamaha PSR-SX700. Key from F4 to B4 are out of tune. Also, when I press on F4 then B4 not making any sound then if I press on B4 then F4 has no sound. My kid spilled some coke on the keyboard few days ago. I already open the keyboard and clean up everything but the issue still there. Please help.

Good chance you caused some damage to the key contact boards underneath the keys. I would suggest to replace the two circuit boards underneath the keys - not expensive at all and whilst replacing them also clean the rubber contacts. These are the part numbers you want:

|ZZ005500|CIRCUIT BOARD|MK-L|MK-Lシート| (ZZ00530)(YJ645B0)|
|ZZ005600|CIRCUIT BOARD|MK-H|MK-Hシート| (ZZ00540)(YJ646B0)|

Thank you for your advised. I will order these Key contact boards to replace the old one. Will let you know how it go. Thank again for your help.

2 key contact boards replaced. Still have same problem. What is the next step should I take to deal with this problem? Please advise. Thanks

That does not make any sense at all!! There is something you are not telling …

What do you call F4 and B4 (counting from left the C = C1) ?

If F4 stops B4 then it should also stop F5 and any combination thereof - as a matter of fact any Fx and Bx because they are on the same scan line. Since you changed the boards there should be no dead diodes now … or did you accidentally re-insert the original boards.

Counting from the left C1 they would be F3-G3-A3-B3. I have a technician to replace the contact board for me. Please check the picture. Keys with X mark are problem. Thank for your help.

… what about the sharps in between ?

All Black sharp keys in between have same issue.

there’s still something missing here:…

See how the selection is made in groups and F3/F#3 (red) is in a different group than G3 … B3(blue).but for polling is made in sections within groups - ie F3 and B3 poll at the same time (green) and F#3 and C3 poll at the same time (purple).
Hence - if F3/F#3 have influence on let’s say B3 the so should C#3, D3, D#3 and E3.

But in any case … since the two boards with the diodes are replaced (the ones underneath the keys) I would suggest the scanner board is the issue …


Anything between the scanner board and the main CPU is serial transmission - it either works or not at all.

Do you know how much is for ZZ503400 CIRCUIT BOARD EMKS for my keyboard. Is it available at Syntaur? Is it easy to replace? I am thinking that I want to do it myself. Thank again for your help

I just had another look at release dates - why are you here?!?!

Released 2019 - that should still be under the 5-year YAMAHA Warranty - unless of course you done bad things to it yourself !!!
That board will be available from YAMAHA and is not expensive either … if not covered under warranty.

To be honest, I do not know this keyboard is still under warranty from Yamaha. I bought this one from a guy, not from the store. Thank you for your advised, I will try to buy the Circuit Board from Yamaha in Canada. Thank again.

Is this ZZ503400 CIRCUIT BOARD EMKS is avaiable at Syntaur? If they do, please provide part number for me. Thank you very much for helping.