panasonic nn-a554w bbtq microwave dead, no power?

this microwave has no power, even though the internal fuses are intact. the symptons are: plug in, no power or display on unit, no internal light, just nothing. i have had this fault in 3 of these inverter type microwave ovens in the past 4 years ! does anyone know what the problem is. probably the main pcb is the problem on all of them. can anyone help please ?