Brother HL-2600CN Service Manual page 339

I-13 White Band
Phenomenon
White banding line appears in the horizontal direction, and consequently causes a
missing image as shown in print sample (13) of Fig.8-2.
Main Causes
1) Installation failure of the transfer unit 2, and deformation of the transfer roller 2.
2) Contact failure of the transfer roller 2 bias pole.
3) Transfer solenoid failure.
Countermeasures
1) Confirm if the transfer unit 2 is properly locked in position and that both ends of the
transfer unit 2 are held by the hooks.
2) Confirm if the transfer unit 2 is properly installed or not.
3) Replace the TR cam clutch 3 with a new one. (See Section 4.2.6 of Chapter VII.)
4) Replace the transfer unit 2 with a new one. (See Section 4.6.1 of Chapter VII.)