I had this happen recently to a 7550 and it was the board which is in the bottom part of the machine. These parts are no longer made, they have to ship them and have them repaired (normally - your guy may be able to do that himself). I just wanted you to be prepared - the estimate for repairing the board was $450. I have 2 other Pfaffs (7550 and 7570) so I decided not to have that one fixed and kept it for parts.