is it still bleeping 4 times?
if so could of damaged pcb but not so common on that model.lid off.looking in from the front the pcb is on your right in a white plastic box with lots of wiring coming from it.BE CAREFUL if you are thinking of replacing it because if the fault is still there and you connect a new pcb it will blow it up and you will of wasted your money yet again!!
CK
April 2012