Oki OKIOFFICE 84, Service Manual

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Service Guide OKIOFFICE 84
Chapter A Board Descriptions
A3.4 P2H Circuit Diagram
This circuit consists of photo-sensors and high voltage generation unit.
Note:
If the high-voltage unit inside the OLHV/TLHV circuit board is replaced, the output voltage and current output
from the terminals must be checked and adjusted. This section does not describe the checking and adjustment
methods, however.
DANGER:
1. High-voltage section
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 R51 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:
Signal Name Output Voltage Application
SB1/SB2 0±5 V/-450 V Voltage applied to toner supply roller. P2H
DB1/DB2 +300 V/-300 V Voltage applied to developing roller. P2H
TR1/TR2 +3.5 kV/-0.75 kV Voltage applied to transfer roller. P2H
CH -1.35 kV Voltage applied to charging roller. P2H
CB1 +400 V Voltage applied to cleaning roller. P6L
CB2 -1.35 kV P6L
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