Brother International HL-1070 Service Manual - Page 69

3.2 Troubleshooting Image Defects The following procedures should be followed in the event of specific image defects. See subsection 3.3 for information about the location of the high-voltage contacts and grounding contacts. I-1 Light Possible cause Density dial Toner sensing failure (printer side) Toner sensing failure (toner cartridge side) Drum connection failure High-voltage power supply PCB failure Driver PCB or main PCB failure Scanner unit failure Step 1 2 3 4 5 6 7 Check Is the density dial in the center of the click position? Can printing be started with the drum unit removed? Is the problem solved when 4 or 5 pages are printed after the toner cartridge is replaced with a full one? Is all the contacts (HV, GND) connected with electrode when the drum unit is installed? Check the harness connection between the high-voltage power supply PCB and the driver PCB. Perform the same check as step 5 above and also between the driver PCB and the main PCB. Is the problem solved by repealing the scanner unit? Result No Yes Yes No No No Yes Remedy Set it to the center detect position. Toner sensor failure. Check if the toner sensor needs cleaning and check the toner sensor connection. The wiper of the toner cartridge is defective. Replace the toner cartridge. Clean contact electrodes both in the printer body and on the drum unit. If the connection is normal, replace the high-voltage power supply PCB. Replace the driver PCB or the main PCB. Replace the scanner unit. HV.GND contacts (Fig.4-5) ➀ IV-5