Brother HL-1850 Service Manual page 235

I-19 Hollow print
User Check
(1) Check the paper used meets the recommended paper specifications.
(2) Select the 'Thick paper mode' in the printer driver, or use thinner paper than you are
currently using.
(3) Check the printer's environment, conditions such as high humidity may cause this
situation to occur.
Possible cause Step
Print paper 1
I-20 Downward fogging of solid black
Possible cause Step
Toner cartridge 1
failure
High-voltage 2
power supply
PCB failure
Check
Is thick paper of more than
43lb being used or extremely
rough surface paper?
Check
Is the problem solved after
replacing the toner cartridge?
Is the problem solved after
replacing the high-voltage
power supply PCB?
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HL-1850/1870N SERVICE MANUAL
Result Remedy
Yes Recommend to use the
specified types of paper.
No Refer and compare with I-15.
Result Remedy
Yes Replace the toner cartridge.
Yes Replace the high-voltage power
supply PCB.