Canon PC300 Service Manual page 52

SS OPERATIONS AND TIMINGS
The microprocessor varies the pulse width of the transfer DC bias control command (DCT-
PWM) according to the internal resistance of the transfer charging roller affected by the sur-
rounding environment, thereby controlling the negative DC bias.
If an overcurrent occurs in the output side of the transformer (T107) because of changes in
the environment, the current limiter circuit exerts control so that no current larger than the speci-
fied value will flow.
c. Operations in Cleaning Mode
TREV=0
eee bias control circuit goes ON.
Multiplier/rectifier circuit goes ON.
SS Cleaning mode is selected, apply-
ing a positive DC bias to the
transfer charging roller.
HVTDC=0, DCTPWM=0
Oscillation circuit goes OFF.
Pulse/DC converter circuit goes OFF.
COPYRIGHT © 1994 CANON INC. CANON PC300320/%25, FC210/290 REV.O JULY 1994 PRINTED IN JAPAN (MPRIME AU JAPON) 3-25