Epson LQ-2550 Technical Manual page 85

of the +35 V line rises and the relationship between VREF and V35E becomes ,,,,
as shown below, the output of EA1 is changed from LOW H I G H .
to
When the output of EA 1 is HIGH, TR 1 and TR2 turn off, and Q3 in main switching circuit 2 turns off.
In this way, the voltage induced in the secondary side of T3 drops. When
starts switching operation again, and turns Q3 on and off.
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