I have a Yamaha P70 digital piano and one F and F# stopped working. Then the adjacent G,A,B,C ansd the sharps inbetween would only work sometimes - ususally after the piano had been on for awhile. The n, after a few weeks, these notes would only work after tapping them alot and when they would finally sound, they would make a very loud note before sounding normal. Now I can't get any of these notese to work at all - like the F and F#.

SOURCE: Yamaha Electronic Piano- certain notes malfunctioning

Either the first or second closure matrix line for the "A" keys is bad.

This may be a cracked or shorted circuit board.

A bank of diodes is used to prevent sneak electrical path if more than one octave has notes pressed.

First thing is to clean ALL the key contact areas and the conductive rubber pills with 99% isoprophyl alcohol.

This involves dis-assembly of the key area. If you are not competent in electronics, best left to a pro shop.

The keys are scanned in a matrix, two contacts per key and all the individual notes are in common (all the "A;s", "B's"...) And each octave is strobed for the first set of contacts and then for the second set of contacts. an the whole octave is read in parallel.

The reason for two contacts is one closes first and then the other as a key is lowered. The time between these is measured and is the note VELOCITY which for a piano controls the loadness of the note. IF ONE of the two fail, the loudness will vary as yours does.

SOURCE: as i play notes on

Check if you MIGHT be in a "guide" or learning mode. Some Yamaha synths have a mode that will play and then wait for you to hit the right key before moving on. If this is not the problem, a fix is not DIY and will require repair. I assume you are NOT using MIDI as in that case it is called "dreaded MIDI drone" and is due to data looping back into the unit which is an external fault.

SOURCE: key doesn't work properlyon yamaha p95 piano

take it back, its still under warranty. That means the key has a contact problem in the circuit. you have to take it all apart, clean it, check the contacts....probably lint. You can try vaccumming it and it might fix the problem. I bought one too and it wasnt good