Toshiba DP120F Service Manual page 410

To supply constant-current to the transfer charger, the I/OP-2 GA causes either of the THVON
and PCU signals to be HIGH. Then Q5 on the HVPS turns on to supply 24VSW to IC3. IC3
causes Q9 to turn on and off and repeat supplying and cutting off of current to the primary
circuit of the transformer (T3). This allows power to be emitted from the secondary circuit of the
transformer and constant-current to be supplied to the transfer charger.
At this time, the value of the current to be supplied is set according to the signal levels of the
THVON and PCU signals.
When the THVON signal is at LOW level and the PCU signal is at HIGH level, Q7 and Q8 on
the HVPS turn on and off respectively to supply +210µA to the transfer charger.
When the THVON signal is at HIGH level and the PCU signal is at LOW level, Q7 and Q8 on
the HVPS turn off and on respectively to supply +180µA to the transfer charger.
When both the THVON and PCU signals are at LOW level, Q5 on the HVPS turns off to cut off
the supply of current.
To supply constant-voltage to the drum, the I/OP-2 GA causes the DRBIAS1 signal to be HIGH.
Then Q10 on the HVPS turns off and Q11 repeats turning on and off to repeat supplying and
cutting off of current to the primary circuit of the transformer (T4). This allows power to be
emitted from the secondary circuit of the transformer and constant-voltage to be supplied to the
drum.
At this time, the value of the voltage to be supplied is set according to the DRBIAS2 signal
output from the I/OP-2 GA.
When the DRBIAS signal is at LOW level, the photo-coupler (PC2) on the HVPS turns on to
supply -100V to the drum.
When the DRBIAS signal is at HIGH level, the photo-coupler (PC1) on the HVPS turns on to
supply -200V to the drum.
When the DRBIAS1 signal is at LOW level, 0V is supplied to the drum.
Constant voltage is supplied to the grid when the anode side of the series of Zener diodes
(ZD4-7) with the cathode side connected to the PG is connected.
Signal Name Type
CHVON O
DEVON O
TCVON, O
PCU
DRBIS1-2 O
March 2000 © TOSHIBA TEC
Active
H Charge Voltage Supply Signal
H Development Roller Voltage Supply Signal
H Transfer Charger Current Set 1/2 Signal
H Drum Bias Voltage Set 1/2 Signal
Description
7-101
Destination
IC52
IC52
IC52
IC52
DP120F/DP125F Circuit Description