Sharp SF-2040, Service Manual, Page: 87 / 131

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
µ
A 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.
c. Check that the difference in current between both sides is
8.0
µ
A or less. If the difference is more than 8
µ
A, 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 Grid voltage
Normal 860 –860V
TSM 755 –755V
Photo 610 –610V
NORMAL (Normal mode)
Set value: 860 = –860V 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: 755 = –755V 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: 610 = –610V output
To decrease the measurement voltage, make the set value
smaller. (1 step: 1V)
To increase the measurement voltage, make the set value
greater.
(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 Output Voltage
Normal mode –860
±
10 V
TSM mode –755
±
10 V
Photo mode –610
±
10 V
N/C
N/O COM
(OFF)
N/C
N/O COM
(ON)
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