Brother International HL-1070 Service Manual - Page 72

I-4 All black Possible cause Corona failure Harness connection H.V. power supply PCB Ditto Main PCB Driver PCB Step Check 1 Is the corona wire of the drum unit broken? 2 Are the electric terminal springs in the printer body and the electrode on the bottom face of the drum unit dirty? 3 Is the scanner unit connected with the driver PCB correctly? 4 Is the problem solved after H.V. power supply PCB replaced? 5 Perform the same check as in step 3. 6 Is the problem solved after main PCB replaced? 7 Is the problem solved after driver PCB replaced? Result Remedy Yes Replace the drum unit. Yes Clean the terminals in the printer and on the drum. Yes Check the harness connection between the scanner unit and the driver PCB. Yes Replace the H.V. power supply PCB. No Replace the panel sensor PCB. Yes Replace the main PCB. Yes Replace the driver PCB. HV.GND contacts (Fig.4-5) ➅ IV-8