Charging Control - Minolta Di551 Service Manual

CORONA UNIT SECTION

[3] Charging Control

C.CONT
EM(C).SIG
TXD
CLK
LATCH
PRCB
MS1
24V2
P.GND
DCPS
The current output to the charging wire and the
voltage applied to the grid are supplied from HV
(high voltage unit) and they are controlled by
PRCB (printer control board).
The levels of outputs to these are transmitted
using 8-bit serial data. This serial data includes
the level information for all outputs driven by HV,
excluding the ON/OFF control signal. Accord-
ingly, a separate signal line is provided to turn
ON/OFF only the charging wire output and the
grid output at the same time.
1. Operation
a. Charging
A Scorotron charging method is used. 24 VDC
supplied from DCPS is raised to a negative DC
voltage which is then discharged after being
applied to the charging wire.
Charge output range: -600 µA to -1200 µA
b. Grid voltage
The grid voltage is output from HV to the charg-
ing plate.
Grid voltage output range: -500 V to -1000 V
2. Signals
a. Input signal
(1) EM (C).SIG (HV to PRCB)
This signal indicates the leak or short state of the
charging corona unit.
[L]: Normal
[H]: Abnormal
CHARGING
HV
MS2
2-F-2
b. Output signals
(1) C.CONT (PRCB to HV)
This signal turns ON/OFF the charging wire.
[L]: Charging voltage ON
[H]: Charging voltage OFF
(2) TXD (PRCB to HV)
Output level of each high voltage electrode.
Serial data signal for control
(3) CLK (PRCB to HV)
Clock signal for TXD
(4) LATCH (PRCB to HV)
Latch signal for TXD