Brother IntelliFax-4750 Service Manual page 198

Trouble
(3) Light
(4) Dark
At the scanner
Check the following components:
- CIS unit
- Main PCB
At the printer side
Replace the toner cartridge with a new one and print 4 to 5
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pages. If the problem persists, proceed to the next step.
Remove the toner cartridge and start printing. If printing
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takes place, clean the toner sensors (LED and light-
receiver), check the sensor harnesses, and then replace the
toner sensor PCBs.
Clean the high-voltage contacts for the transfer roller on the
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drum unit, main cover, and high-voltage power supply PCB.
...
(Contacts in the illustration given on page VI-27)
Clean the high-voltage contacts for the developer roller on
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the drum unit, main cover, and high-voltage power supply
ƒ
PCB. (Contacts
Clean the grounding contacts on the drum unit and main
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•
cover. (Contacts
Check the connection of the main PCB and high-voltage
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power supply PCB.
Replace the drum unit.
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Replace the high-voltage power supply PCB.
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Replace the engine PCB.
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Replace the main PCB.
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Replace the laser unit.
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At the scanner
Check the following components:
- CIS unit
- Main PCB
At the printer side
Slide the wire cleaner to clean the corona wire inside the
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drum unit.
Clean the high-voltage contacts for the grid and charger on
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the drum unit, main cover, and high-voltage power supply
„
PCB. (Contacts
VI-27)
Replace the toner cartridge.
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Replace the drum unit.
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Replace the high-voltage power supply PCB.
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Replace the main PCB.
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Replace the engine PCB.
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VI - 21
Action to be taken
in the illustration given on page VI-27)
in the illustration given on page VI-27)
‚
and in the illustration given on page