Why is my keyboard stuck on one tone

Yestday I bought a Yamaha keyboard from a carboot for £5.00 when I got home I went up stairs and plunged it in the kayboard has got Some problems I would like some help on how to fix them here are the problems

When I first plunged the keyboard into the mains and switched on the power it firstly plays a bunch of notes at the same time when the power button is tuned on also two keys arcoss the Intier keyboard have no function at all. The keyboard seems to be stuck on one tone no over function seem to want to work. The ldc screen is also got a wired problem with it to part of the lines for the counter are missing too.

Please can some one give so advice on how I can go about fixing this thank you.