Brother 8250P - FAX B/W Laser Printer Service Manual page 169

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 sensor or replace the toner
sensor PCB.
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 ƒ in the illustration given on page VI-21)
Clean the high-voltage contacts for the developer roller on
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the drum unit, main cover, and high-voltage power supply
PCB. (Contacts ‡ in the illustration given on page VI-21)
Clean the grounding contacts on the drum unit, gear drive
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unit, and main cover. (Contacts • and ‚ in the illustration
given on page VI-21)
Check the connection of the main–high-voltage flat cable.
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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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At the scanner
Check the following components:
- CIS unit
- Main PCB
At the printer side
Slide the wire cleaner tab to clean the corona wire inside the
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drum unit.
Clean the high-voltage contacts for the grid and corona wire
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on the drum unit, main cover, and high-voltage power supply
PCB. (Contacts ... and † in the illustration given on page
VI-21)
Replace the drum unit.
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VI - 17
Action to be taken