yamaha psr 350 keyboard none of the keys have sound

I would have a look at the ribbon connector from the keys to the circuit board. Check it is in place and not loose. Also, dies the demo work? or the drums... Is there any sound at all out of the speakers? (even a low hiss?)

If demo or drums sound then that's good news... means that the d to a converter is working and the digital side is ok. Worst case is the keyboard interface chip (not common).. If no sound at all then it could be the power amp.

more info needed.

I have a little sound but statics