OKIDATA OF1050, Service Manual

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Service Guide OF1050/2350/2450
Chapter 3 Board Description/Printer Operation
3.9.02 Power Supply Unit (FXVE/FXVH)
General functional description
1. General
The power supply unit consists mainly of an AC transformer and a power PCB (FXVE board for
AC120V/FXVH board for AC230V). A block diagram of the power supply unit is shown in Figure A3.XX.
The power PCB is composed of five main circuits: AC input section, heater control section, low-voltage
section, high-voltage section and protection circuit.
The low-voltage section provides a +5V output by a DC-DC converter and other output voltages (+30V,
+8V and -8V) simply by rectifying and smoothing the respective outputs of the AC trans-former. The
high-voltage section (TR1, TR2, DB1, DB2, SB2, CB and CH) produces a flyback voltage from 5V by
using a drum coil and a high-voltage transformer.
2. Circuit description
AC input section
AC commercial power is supplied to line filter circuit through the AC inlet, power switch (SW1) and the
fuse (F1). Fuse F1 is used for protecting the heater circuit.
Fuse F2 is used to protect the secondary circuit from overvoltage from the AC input line. This fuse F2 is
not mounted in the power supply unit for 230VAC input.
Heater control circuit
The on/off operation of the heater is controlled by the operation of photocoupler PC1 whose operation is
controlled by the HEAT-N signal applied to CN3-20 pin from the control PCB (R054R050/R175/R175-2
board).
3. Low-voltage section
+30 V circuit
This circuit pr30 V output by rectifying the corresponding output of transformer T1 and smoothing
the rectified signal by capacitor C7.
+/- 8 V circuit
This circuit pr8 V and -8 V outputs by rectifying the corresponding output of transformer T1,
smoothing the rectified signals by capacitors C13 and C14.
+5 V circuit
This circuit pr5 V output using output by means of DC-DC converter circuit.
4. Protection circuits