Brother MFC-7420 User Manual

Troubleshooting and routine maintenance
11 - 17
11
All black
Clean the primary corona wire on the drum unit. (See Cleaning the corona wire on
page 11-24.)
If the print quality has not improved, install a new drum unit. (See Replacing the
drum unit (DR-2025) on page 11-28.)
White Spots on black text and
graphics at 78.5 mm
intervals
Black Spots at 78.5 mm
intervals
Cleaning the drum unit
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 copies
on page 8-2.)
1 Remove the drum unit and toner cartridge assembly, and then remove the toner
cartridge from the drum unit.
2 Position the print sample in front of the drum unit so you will know the exact
position on the drum that is causing the poor print.
3 Turn the black gear on the drum as you check the surface of the OPC drum.
Do not touch the OPC drum with your fingers.
4 When you find the substance on the drum surface that matches the print
sample, gently dab the surface of the OPC drum with a cotton swab that is lightly
dampened with isopropyl alcohol.
Do not use a scrubbing or wiping motion because this might damage the
drum.
Do not try to clean the surface of the OPC drum with a sharp object, such as
a ball-point pen, because this might cause permanent damage to the drum
unit.
If the print quality still has not improved you need to install a new drum.
(See Replacing the drum unit (DR-2025) on page 11-28.)
Examples of poor print quality Recommendation
78.5 mm
78.5 mm
78.5 mm
78.5 mm
OPC drum surface

Brother MFC-7420 Specifications

General

Print technology	Laser
Maximum resolution	600 x 2400 DPI
Time to first page (black, normal)	10 s
Print speed (black, normal quality, A4/US Letter)	20 ppm
Maximum print size	210 x 297 mm
Maximum ISO A-series paper size	A4
Scanner type	Flatbed scanner
Grayscale levels	64
Input color depth	24 bit
Maximum scan resolution	9600 x 9600 DPI
Maximum copy resolution	600 x 300 DPI
Copy speed (black, normal quality, A4)	20 cpm
Faxing	Mono faxing
Fax memory	400 pages
Modem speed	14.4 Kbit/s
Auto-redialing	Yes
Fax speed dialing (max numbers)	200
Total input capacity	250 sheets
Auto document feeder (ADF) input capacity	35 sheets
Internal memory	16 MB
Sound pressure level (printing)	53 dB
Dimensions (WxDxH)	432 x 395 x 294 mm
All-in-one functions	Fax, Scan
Standard media sizes	A4, LTR, EXE, A5, A6, B5, B6
Media types supported	Plain, Recycled, Envelopes, Transparency, Bond, Labels
Color all-in-one functions	scan, n
Compatible operating systems	Windows 98/98SE/Me/2000/NT/XP Mac OS 9.1-9.2 + Mac OS X 10.2.4
Standard interfaces	Parallel, USB 2.0
Parallel ports quantity	1
Maximum duty cycle	10000 pages per month
Operating relative humidity (H-H)	20 - 80 %
Package weight	14500 g
Market positioning	Home & office