Problems with Yamaha PSR 275

by Terry
(Penistone, England)

A year or so ago I bought the above keyboard. I played around with it for a while and after about 6 months put it under my bed and forgot about it until this weekend when I had another urge to learn to play. After dusting off the board I switched on the power the light to the display came on and then - nothing. No matter what key was pressed the only noise that came from the unit was mains hum from the speakers.
The keyboard was working well when it was put under the bed, it was not abused while it was there. Is there some item in the hardware that degenerates when the board is not used? Could anyone tell me of a test I might carry out to give me a clue as to what is the problem?
Regards
Terry