Sony S75F Service Manual page 34

Rectifier and filter circuit: The AC input is changed to a high DC voltage, that magnitude is the product of
1.414 to AC after it is commuted by bridge rectifier (BD901) and filtered by the capacitance (C905).
Start-up circuit: After being commuted and filtered, the high DC voltage falls down through R (R904, R908,
and R911 series), the start-up carries out when the lowered voltage is supplied to L Pin of IC901
(TOP247Y). The output pulse makes T901 work. The voltage produced at the two terminals of T901
is offered to C Pin of IC901 after being commuted by D905 and filtered by C914, and then the whole
start-up process is end.
Over-voltage Protection circuit:
1. ZD903 can be broken down when12V DC voltage increases, which leads to the current
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S75F Sony