Brother MFC620CN Service Manual page 338

Recording paper
Check that:
(1) A recommended type of recording paper is used.
(2) The recording paper is not dampened.
Ink cartridges
(1) Check that all of four ink cartridges are loaded.
Head/carriage unit
(1) Check that the carriage-head flat cable is connected to the carriage PCB.
(2) Repeat the head purging operation several times.
(3) Clean the print surface of the head/carriage unit. (Refer to the User's Guide.)
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