Brother MFC 8420 User Manual

TROUBLESHOOTING AND ROUTINE MAINTENANCE   22 - 19
White Spots on black text 
and graphics at 94 mm 
(3.7 in.) intervals
Black Spots at 94 mm 
(3.7 in.) intervalsIf the problem is not solved after printing a few pages, the drum unit may 
have glue from label stock on the OPC drum surface.
Clean the drum unit as follows:
1 Position the print sample in front of the drum unit, and find the exact 
position of the poor print.
2 Turn the drum unit gear by hand while looking at the surface of the 
OPC drum.
Do...

22 - 20   TROUBLESHOOTING AND ROUTINE MAINTENANCE
Black toner marks across 
the pageThe drum unit may be damaged. Put in a new drum unit. (See Replacing 
t h e d r um  u ni t on page 22-34.)
Make sure that you use paper that meets our specifications. (See About 
paper on page 2-1.)
If you use label sheets for laser printers, the glue from the sheets may 
sometimes stick to the OPC drum surface. Clean the drum unit. (See 
Cleaning the drum unit on page 22-27.)
Do not use paper that has clips or staples...

TROUBLESHOOTING AND ROUTINE MAINTENANCE   22 - 21
Wrinkles or creasesMake sure that paper is loaded properly.
Check the paper type and quality. (See About paper on page 2-1.)
Try printing using the straight-through output path. (See How to load 
paper on page 2-5.)
Turn over the stack of paper in the tray or try rotating the paper 180° in 
the input tray.
The drum unit is a consumable item and it is necessary to 
replace it periodically.
Examples of poor print 
qualityRecommendation
B DEFGH
abc efghijk...

22 - 22   TROUBLESHOOTING AND ROUTINE MAINTENANCE
Packing and shipping the MFC
Whenever you transport the MFC, use the packing materials that 
came with your machine. If you do not pack t he MFC correctly, you 
may void your warranty.
1Turn t he MFC power swit ch off.
2Unplug the MFC from the telephone wall jack.
3Unplug the MFC from the AC outlet.
Lock the Scanner Lock
4Push the Scanner Lock Lever down to lock the scanner. This 
lever is located on the left of the scanner glass.
Caution
Damage caused to...

TROUBLESHOOTING AND ROUTINE MAINTENANCE   22 - 23
6Remove the drum unit and t oner cartridge assembly. Leave the 
t oner cartridge installed in the drum unit.
7Place the drum unit and toner 
cartridge assembly into the plastic bag 
and seal the bag.
8Close the front cover. Fold down t he face-down output  tray flap. 
Remove t he telephone line cord.
9Wrap the MFC in the plastic bag 
and place it in t he original carton 
with the original packing material.
 

22 - 24   TROUBLESHOOTING AND ROUTINE MAINTENANCE
10Pack the drum unit and t oner cartridge assembly, telephone line 
cord, AC cord and printed materials in the original carton as 
shown below: 
11Close t he carton and tape it shut.
If you are returning the MFC to Brother as part of the Exchange 
Service,  pack only the MFC. Keep all separate parts to use with 
your ‘Exchange’ machine.
 

TROUBLESHOOTING AND ROUTINE MAINTENANCE   22 - 25
Routine maintenance
Cleaning the scanner
Turn the MFC power switch off and lift the document cover. Clean the 
scanner glass and glass strip with dry clot h and the white film with 
isopropyl alcohol on a lint free cloth.
If t he screen still displays a scanner error,  call Brother Customer 
Service for assistance at 1-800-284-4329 (in USA) or 
1-877-BROTHER (in Canada).
White Film
Document Cover
Glass strip
White film
 

22 - 26   TROUBLESHOOTING AND ROUTINE MAINTENANCE
Cleaning the printer
Caution
■Do not use isopropyl alcohol to remove dirt from the cont rol 
panel. It may crack the panel.
■Do not use isopropyl alcohol to clean the laser scanner window.
■Do not touch t he scanner window with your finger.
■The drum unit contains toner,  so handle it carefully. If toner 
scatters and your hands or clothes get dirty, immediately wipe or 
wash it off with cold water.
1Turn t he MFC power swit ch off and open the front...

TROUBLESHOOTING AND ROUTINE MAINTENANCE   22 - 27
Cleaning the drum unit
We recommend placing the drum unit and toner cart ridge assembly 
on a cloth or large disposable paper to avoid spilling and scattering 
toner.
1Clean the primary corona wire inside the drum unit by gent ly 
sliding the blue tab from right  to left several t imes.
2Return the blue tab and snap it into the Home position (▼). 
Caution
If t he blue tab is not at Home posit ion (▼), printed pages may have 
vertical stripes.
3Reinstall...

22 - 28   TROUBLESHOOTING AND ROUTINE MAINTENANCE
Replacing the toner cartridge
The MFC can print up to 6,500 pages using a high yield toner 
cartridge. When the toner cartridge is running low, the LCD shows 
Toner Low. The MFC is supplied with a standard toner cartridge 
that must be replaced after approximately 3,300 pages.  Actual page 
count  will vary depending on your average t ype of original (i.e., 
standard let ter, detailed graphics).
Discard the used toner cart ridge according to local...