Brother MFC4820C Service Manual page 190

Trouble
(7) Print edges not aligned
(8) Ink splash
(9) Random missing dots
At the printer
• Check the alignment of vertical print lines in monochrome
and in two colors and the head skew, by using the
maintenance-mode function code 65. (Refer to Chapter 7,
Section 7.5.13).
• Check the print head unit.
• Check the CR encoder strip for stains or scratches. (If the CR
encoder strip is not hooked properly, correct it.)
• If you replace the print head unit, make the necessary
adjustments. (Refer to Chapter 6, Section 6.1.2.)
At the printer
• For each of the four ink colors, perform the head purging
operation several times to remove dust or air bubbles from its
nozzles.
• Check the ink cartridges. If any of them has run out of ink or
the ink viscosity has been increased, replace it.
• Replace the print head unit.
• Replace the main PCB.
• Replace the power supply PCB.
• Check that the print head unit is installed to the carriage
correctly.
At the printer
• For each of the four ink colors, perform the head purging
operation several times to remove dust or air bubbles from its
nozzles.
• Check the ink cartridges. If any cartridges have run out of ink,
replace them.
• Replace the print head unit.
(If the problem persists, replace the carriage ASSY.)
• Check the connection of the head flat cables on the main PCB
and print head PCB. (If either of the head flat cables is broken
or damaged, replace the needle tube & head flat cable ASSY.)
• Replace the main PCB.
• Clean the head caps and wiper of the purge unit with a
Rubycel stick. For the cleaning procedure, refer to "Cleaning
the purge unit" given on page 8-22.
8 -1 9
Action to be taken