Oki OKIFAX4550, Maintenance Manual

Page: 354 / 592

41309401TH Rev.4
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7.1 High-voltage section
7.1.1 Functional overview
The high-voltage outputs consist of TR1 (3.9 kV), TR2 (-0.75 kV), DB1 (+265 V), DB2 (-265 V), SB2
(-550V), CB1 (+400 V), CB2 (-1.35 kV) and CH (-1.30 kV) and are obtained as follows. The control
signal obtained from IOGA4 of R46 board is applied to High-voltage power supply circuit. As result,
the driver current is applied to the drive circuit, which will provide the high-voltage outputs.
Note:
7.1.2 SB2, DB1, DB2 (P2H)
1) These four high-voltage outputs are obtained from the flyback voltage of Q10.
2) The positive and negative voltages of DB1 and DB2 are obtained by switching the charging
direction under the triac and thyristor.
3) Feedback is not applied to these outputs. However, SB2 is limited by D85 and DB2 is limited
by D84 so as not to provide an output exceeding a preset voltage.
7.1.3 TR1 and TR2 (P2H)
1) The TR1 high-voltage is obtained by rectifying the secondary output of Q17 switching circuit by
a voltage-doubler rectifier.
2) TR1 output circuit has both constant current (hereinafter called CC) and constant voltage
(hereinafter called CV) modes.
3) At first, TR1 output circuit operates in the CC mode. Once the voltage determined by parameters
such as roller and medium is obtained, this circuit changes to operate in the CV mode by the
control signal.
4) The TR2 output voltage is regulated by keeping the voltage obtained by switching operation of
Q15 at a constant voltage by D66 and D65.
7.1.4 CH (P2H)
1) The CH output voltage is stabilized by keeping the primary flyback voltage obtained by switching
operation of Q16 at a constant voltage by D76 and D82.
7.1.5 CBI, CB2 (P6L)
1) The CB1 output voltage is stabilized by keeping the primary flyback voltage obtained by
switching operation of Q2 at a constant voltage by D7 and D6 and D5.
2) The CB2 output voltage is stabilized by keeping the primary flyback voltage obtained by
switching operation of Q1 at a constant voltage by D7 and D6 and D5.
Signal Name
SB1/SB2
Output Voltage
0–5 V/-550 V Voltage applied to toner supply roller.
Voltage applied to developing roller.
Voltage applied to transfer roller.
Voltage applied to charging roller.
Voltage applied to cleaning roller.
+265 V/-265 V
+3.9 kV/-0.75 kV
-1.30 kV
+400 V
Application Board
DB1/DB2
TR1/TR2
CH
CB1
Voltage applied to cleaning roller.
P2H
P2H
P2H
P2H
P6L
P6L -1.35 kV
CB2