OKIDATA OF1050, Service Manual

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The protection circuit includes fuse F3 for +30 V and +5 V for overcurrent protection.
If an overvoltage is applied to the +5 V circuit, fuse F3 will blow.
F1 will blow only in the event of AC line shortcircuit.
5. Cover open circuit
The cover open circuit consists of SW2, Q24 and Q25. When the stacker cover is opened, the cover open
microswitch (SW2) on the FXVE/FXVH board is turned off to cut the supply of 5V to the high-voltage
power supply circuit. As a result all high-voltage outputs are interrupted. At the same time, a signal is sent
to the control board to notify it the off state of the microswitch, and the control board performs the cover
open processing, and display message.
6.. High-voltage section
Functional overview
The high-voltage outputs consist of TR1 (1 kV), TR2 (-0.75 kV), DB1 (+300 V), DB2 (-300 V), SB2
(-450V), CB (+400 V) and CH (-1.35 kV) and are obtained as follows. The control signal obtained from
connector CN3 is applied to power control IC2. As result, the driver current from this IC2 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.
DB1/DB2 +300 V/-300 V Voltage applied to developing
roller.
TR1/TR2 +1 kV/-0.75 kV Voltage applied to transfer
roller.
CH -1.35 kV Voltage applied to charging
roller.
CB +400 V Voltage applied to cleaning
roller.
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