Oki OKIOFFICE 84 Service Manual page 419

provide an output exceeding a preset voltage.
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.
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.
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.
2. Photosensors
The photosensors mounted on this circuit board/sensor board supervise the paper running state during printing.
These four photosensors are used in this printer as listed below. All of their outputs enter IOGA4 for referring to and
processing by the IOGA4 (CPU).
1) PS1 (photosensor 1): TNRSNS
Detects the lack of the toner.
2) PS2 (photosensor 2): PSIN
Detects the leading part of the paper and gives the supervision timing for switching from hopping operation to
feeding operation. Supervises the paper running state and the paper size according to the paper arrival time and
running time.
3) PS3 (photosensor 3): PSOUT
Supervises the paper feed according to the time of arrival at the sensor and the time of passage of paper.
4) PS4 (photosensor 4): WRSNS
Detects the leading part of sensor.
Supervises the paper running state.
3. Cover open circuit
The cover open circuit consists of CVSW. When the Cover-Main is opened, the cover open microswitch (CVSW) on
the OLHV/TLHV board is turned off to cut the supply of H5V to the high-voltage power supply circuit. As a result all
high-voltage outputs are interrupted. At the same time, the CVOPN-N 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.