Brother MFC640CW Service Manual page 225

The "EXIT ADJ NO. +0" appears on the LCD.
(12) Check the PF adjust check patterns ("B" on
uneven print. Make a note of that pattern number.
(13) Enter the number of the least uneven check pattern found in step (11).
The machine automatically returns to the initial stage of the maintenance mode.
page 8-28) and select the one that is the least
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