Yamaha W5 keybed

I have a Yamaha w7 with a weird issue. Only the top two or perhaps 3 keybed octaves are working. I’ve rest all connectors. Any ideas ?

Sounds like a loose cable either from the cable that joins the 2 sections of switch boards or runs to the main board

Unfortunately it’s not a loose cable. Everything is seated properly. Checked the cable continuity, key-bed diodes and connectors, re soldered the connectors.

I noticed when everything is connected and i play the lower octaves, it activated some buttons functions. Thought there might be a short circuit somewhere.

Issue still persists.

In this case it sounds like a main board ptoblrm. Of couse this is NLA. I could email you the SM if you nned it

Thank you. I’ll give it a try or two, if not the it will end up for parts. I have a suspicions it is a short somewhere on the scanning circuity because when i disconnect the keybed, the buttons work perfectly and when i connect it back, they behave oddly

Found the cause, badly leaking 220uf 16v caps. They l’ve damaged the board.

So i replaced some and it started working. Then whn continues with the rest, now the system doesn’t noot successfully every time. I checked all the work i’ve done and also surround traces nd components. Found nothing. All voltages are good and no ripples.

Any Ideas on how to approach this methodically , like looking for certain signals ??