Sharp FO-3150 Service Manual page 87

d. High voltage unit control
The high voltage unit outputs the following voltages:
• Main charger voltage (DC-950V + AC600V peak to peak)
• Transfer charger voltage (DC+2100V + AC600V peak to peak)
• Developing bias voltage (DC-390V)
The following signals are outputted from the CPU (ASIC) to control the
above voltages.
• MCON
This signal is to turn on/off the main charger.
When this signal is outputted, Q7 is driven to the high impedance state.
Then Q9 conducts to drive transformer T2.
As a result, the main charger voltage is outputted to the secondary
side of the transformer.
• TC/BIASON
This signal is to turn on/off the transfer charger and the developing
bias voltage.
When this signal is outputted, Q3 is driven to the high impedance state.
former.
• PWMSIN
This signal is to control the main charger voltage and the transfer
charger voltage. The PWM pulse of 288.76Hz is outputted.
This pulse waveform adds the AC component to the main charger volt-
age and the transfer charger voltage.
By changing the pulse duty of this signal, the main charger voltage
and the transfer charger voltage are controlled (during temperature
correction operation).
When the pulse duty of this signal is changed, the collector currents of
Q4 and Q8 are changed. Therefore, the base current of Q9 and the
drive current of transformer T2 are changed to change the main charger
voltage and the transfer charger voltage.
R29, R31, C19, and C20 from a filter circuit which dulls the waveform
of PWMSIN signal.
e. Electrical connection
CONTROL PWB
8bit CPU
IC9
58
TC/Bias ON
56
ASIC
129
IC8
PRINTER PWB
MCON 5 12
IC1
3 14
PW MSIN
Q4
CNPRT
Q7 Q9
T2
Q8
Transformer
+24VP
+24VP
Q3 Q5
T1
Transformer
Q6
Fig. 13
5 – 14
FO-3150U/C
Charger
roller
MC
OPC
DRUM
Separation electrode
TC
Transfer roller
100V Doctor
DC
Bias
Developing
roller
Supply roll i er