Sharp FO IS125N - B/W Laser - All-in-One Service Manual page 113

3. Printer mechanism control block
3.1. Unit control
3.1.1 High voltage unit control
The high voltage unit outputs the following voltages:
• Main charger voltage (DC-950V + AC760V peak to peak)
• Transfer charger voltage (DC+3600V + AC760V peak to peak)
• Developing bias voltage (DC-200V)
The following signals are outputted from the CPU and Logic to con-
trol the above voltages.
• MCON
This signal is to turn on/off the main charger.
When this signal is outputted.
As a result, the main charger voltage is outputted to the secondary
side of the transformer (B51).
• TCON
This signal is to turn on/off the transfer charger and the developing
bias voltage.
• PWMSIN
This signal is to control the main charger voltage and the transfer
charger voltage. The PWM pulse of about 300Hz is outputted.
This pulse waveform adds the AC component to the main charger
voltage and the transfer charger voltage.
By changing the pulse duty of this signal, the main charger voltage
and the transfer charger voltage are controlled.
3.1.2 Electrical connection
CONTROL PWB
22
TCON
FAX
ENGINE
IC100
21
MCON
27
PWMSIN
High Voltage PWB Unit
Constant
voltage Oscillation B1
control circuit Transformer
circuit
Feedback circuit
Short
protection
circuit
Constant
voltage Oscillation B51
control circuit Transformer
circuit
Feedback circuit
PWM
control
circuit
HV(+)
250MΩ
Rectifier
circuit
HV(-)
Rectifier
circuit
Constant
voltage(-)
circuit
Short
circuit
HV(-)
Rectifier
circuit
Constant
voltage(+)
circuit
Fig. 8
5 – 22
FO-IS125N
LASER MFP
Transfer Roller
TC
OPC DRUM
Separation electrode
Supply Roller
SV
Developing Roller
DV
Doctor
Charger Roller
MC
Heat Roller
FU-EARTH
Pressure Roller