Yamaha has a self-diagnostic program built into the keyboard. It's very effective, and pretty much pinpoints the problems. However, like nearly all, built-in, diagnostic programs it cannot tell you which component on the circuit board is defective. But, it will point you in the right direction.

Cheers,

Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!

K+E=W (Knowledge Plus Experience = Wisdom.)