Brother MFC 9840CDW User Manual

Troubleshooting and routine maintenance
119
C
Improving the print qualityC
If you have a print quality problem, print a test page first (Menu, 4, 2, 3). If the printout looks good, 
the problem is probably not the machine. Check the interface cable or try the machine on another 
computer.
Note
You can resolve a print quality problem by replacing a toner cartridge with a new one when the 
LCD shows the Toner Life End message.
 
Examples of poor print 
qualityRecommendation
White lines or bands or ribbing...

120
Coloured streaks or bands 
down the page
 
„One of the toner cartridges may be damaged. Replace the toner 
cartridge that matches the colour of the streak or bond.
„Clean all four corona wires (one for each colour) of the drum unit by 
sliding the green tab. (See Cleaning the corona wireson page 155.)
„Make sure each corona wire’s green tab is at the home position (b).
„The drum unit may be damaged. Put in a new drum unit. 
(See Replacing the drum uniton page 174.)
„The fuser unit may have a smudge...

Troubleshooting and routine maintenance
121
C
Coloured spots at 75 mm
 
„Dust, paper powder, glue, and so on may stick to the surface of the 
photosensitive drum (OPC) and cause black or white spots to appear 
on printed documents.
„Make a few copies of a blank, white sheet of paper. (See Making 
multiple copieson page 78.)
„If you still see the spots on printed documents after making multiple 
copies, clean the drum unit (See Cleaning the drum 
uniton page 159.)
„If the print quality still has not...

122
Ghost
 
„Make sure that you use paper that meets our specifications. Rough-
surfaced paper or thick paper may cause the problem. 
(See Acceptable paper and other mediaon page 11.)
„Make sure that you choose the correct media type in the printer driver 
or in the machine’s Paper Type menu setting. (See Acceptable paper 
and other mediaon page 11 and Basic tab in the Software User’s 
Guide on the CD-ROM.)
„The drum unit may be damaged. Put in a new drum unit. 
(See Replacing the drum uniton page 174.)...

Troubleshooting and routine maintenance
123
C
Colour misregistration
 
„Make sure that the drum unit is installed properly. (See Replacing the 
drum uniton page 174.)
„Make sure that the belt unit is installed properly. (See Replacing the 
belt uniton page 181.)
„Make sure that the waste toner box is installed properly. 
(See Replacing the waste toner boxon page 186.)
„Perform the auto colour registration by using the control panel. Press 
Menu, 4, 7, 1.
or
„Perform the manual colour registration by...

124
Uneven density appears 
periodically across the page
 
„Identify the colour that is uneven and put in a new toner cartridge for 
that colour.  (See Replacing a toner cartridgeon page 169.)
„The drum unit may be damaged. Put in a new drum unit. 
(See Replacing the drum uniton page 174.)
„Make sure that the fuser unit is installed properly.
Missing image at edge
„Make sure that the toner cartridges are installed properly. 
(See Replacing a toner cartridgeon page 169.)
„Make sure that the drum unit is...

Troubleshooting and routine maintenance
125
C
Offset image
 
„Check the machine’s environment. Conditions such as high 
temperatures and humidity can cause this problem. (See Choosing a 
locationon page 98.)
„Make sure that you use paper that meets our specifications. 
(See Acceptable paper and other mediaon page 11.) 
„Make sure that you choose the correct media type in the printer driver 
or in the machine’s Paper Type menu setting. (See Acceptable paper 
and other mediaon page 11 and Basic tab in the...

126
Curled or wave
 
„Make sure that you choose the correct media type in the printer driver 
or in the machine’s Paper Type menu setting. (See Acceptable paper 
and other mediaon page 11 and Basic tab in the Software User’s 
Guide on the CD-ROM.)
„Check the paper type and quality. High temperatures and high 
humidity will cause paper to curl.
„If you do not use the machine often, the paper may have been in the 
paper tray too long. Turn over the stack of paper in the paper tray. 
Also, fan the paper...

Troubleshooting and routine maintenance
127
C
Envelope creases
 aOpen the back cover.
bPull down the two grey levers, one on the left-hand side and one on 
the right-hand side to the envelope position, as shown in the 
illustration below.
 
cClose the back cover and re-send the print job.
Note
When you have finished printing, open the back cover and reset the 
two grey levers back to the original position.
 
Examples of poor print 
qualityRecommendation
ABCDEFGEFGHIJKLMN
 

128
White lines or ribbing down the 
page on duplex print
 
Note
Position B is only for duplex 
printing with recycled paper 
when the temperature and 
humidity are low.
 
„Choose Thin Paper mode in the printer driver and re-send the print 
job.
If the problem is not solved after printing a few pages, follow these 
steps:
aOpen the back cover.
bPull down the two grey levers, one on the left-hand side and one 
on the right-hand side, to position B as shown in the illustration 
below.
 
cClose the back...