Make sure the door switch interlock switches are being actuated. If they are and you are getting ac voltage into the machine it is probably the power supply board. I would guess about $300-$400.00. I don't think that parts are available anymore for this machine. You may be able to find someone to repair it for about half the cost.
Bill T.
March 2007
I can answer this question...
Sharp SF7800 The machine is totally dead. Nothing lights up?