Yamaha MR-1 playcard system Sound Problem

When I turn on the power, and press the pedal, all I hear is a prolonged instrument even if I haven't presssed any of the keyboard keys. Then if I turn OFF the power, and turn it back on, without having touched any of the instrument buttons or keys, a different prolonged instrument is heard. How do I fix this problem? If I try and press any of the keys, there is no sound from the keys, just the long prolonged instrument sound. Is there something wrong with the circuitry? How do I get this repaired? Is there a repair manual I could follow to repair this problem? I received this for free, so I don't want to have to spend too much to fix it but it would be great if I could get it to work. Thanks!