Checking The Electrostatic Main Charger Current; Adjusting The Electrostatic Main Charger Grid Voltage - Sharp SF-2025 Service Manual

C. Checking the Electrostatic Main Charger Current
The drum current difference(balance) between the sides of front
and rear frame is checked.
1 Perform steps.
2 Clean the saw-tooth plate of the main charger with polystyrene
foam and attach the main charger to the machine.
(Do not attach the transfer/separation charger).
Manually turn on the door switch.
3 Measure the drum current on the sides of front and rear frame.
The difference in current between the front and rear frame must
be 8.0 µA or less.
a. Turn on the main switch and perform Simulation "8-02".
(MHVG will be ON for approx. 30 seconds.)
b. Measure the drum current on the front and rear frame side.
•
If the microswitch is OFF, the drum current on the side of
front frame is indicated.
•
If the microswitch if ON, the drum current on the side of
rear frame is indicated.
(OFF)
N/C
N/O COM
c. Check that the difference in current between both sides is
8.0 µA or less. If the difference is more than 8 µA, replace
the charger unit.
D. Adjusting the Electrostatic Main Charger Grid Voltage
1 Turn off machine. Attach the developing unit and the drum
holder unit to the machine.
(Do not use the electrode sheet).
2 Attach the main charger unit to the machine. The machine
should have all the charger units installed.
3 Turn on the main switch and check the grid voltage using Test
command 44-11.
The grid voltage is displayed in two digits on the copy quantity
display. The display changes in the sequence of N → TSM → P
mode when the message feed key is pressed.
Mode Figure
Normal 56
TSM 52
Photo 50
NORMAL (Normal mode)
Set value: 650 = –650V output
To decrease the measurement voltage, make the set value
smaller. (1 step: 1V)
To increase the measurement voltage, make the set value
greater.
T/S (TSM mode)
Set value: 550 = –550V output
To decrease the measurement voltage, make the set value
smaller. (1 step: 1V)
To increase the measurement voltage, make the set value
greater.
PHOTO (Photo mode)
Set value: 440 = –440V output
To decrease the measurement voltage, make the set value
smaller. (1 step: 1V)
To increase the measurement voltage, make the set value
greater.
(ON)
N/C
N/O COM
Grid voltage
–650V
–550V
–440V
7 – 5
(Measure at check point CP-GB)
4 Remove the rear cover.
5 Connect the digital multimeter to the grid voltage pin (GB).
6 Set the measuring range of the digital multimeter to DCV.
(Use the digital multimeter with measuring range of up to 1000
Vdc).
7 Turn on the front cover switch manually.
8 There is another method to check the grid votage as follows:
Turn on the main switch, and adjust the output adjusting control
so that output voltage values in Simulation "8-02"(normal mode),
"8-03"(photo mode) and "8-04"(TSM mode) are as follows:
TEST POINT CP-GB
Normal mode
TSM mode
Photo mode
Output Voltage
–650±5V
–550±5V
–440±5V