Brother MFC-7840W Service Manual

1-40
Confidential
■ Black spots
■ Black band
User Check
• Damp (wet) paper might be used. Try to change to freshly unpacked
paper.
• Toner may be empty. Replace the toner cartridge with a new one.
• If the problem is not solved after printing a few pages, the drum unit
may have glue from label stuck on the exposure drum surface.
Refer to the previous page, and wipe it off gently with a cotton swab.
• The drum unit may be damaged. Replace the drum unit with a new
one.
Step Cause Check
Result Remedy
1
Toner attached
on the develop
roller
Are the black spots at
40.6 mm (develop roller
circumference)
intervals?
Ye s
This problem will
disappear by printing
approximate 10 pages. If
the same problem occurs,
replace the toner cartridge.
2
Scratch and Dirt
on the exposure
drum
Are the black spots at
75.0 mm (exposure
drum circumference)
intervals?
Ye s
Replace the drum unit.
3
Drum unit
connection
failure
Are the electrodes on
the drum unit and
machine body dirty?
Ye s
Clean both electrodes
(Refer to Fig. 1-1, Fig. 1-2.).
4
Scratch and Dirt
on the heat roller
Are the black spots at
78.5 mm (heat roller
circumference)
intervals?
Ye s
Replace the fuser unit.
5
HVPS PCB
failure
Is the problem solved
after replacing the
HVPS PCB ASSY?
Ye s
Replace the HVPS PCB
ASSY.
6
Main PCB failure Is the problem solved
after replacing the main
PCB ASSY?
Ye s
Replace the main PCB
ASSY.
User Check
• Clean the inside of the machine and the corona wire in the drum
unit. If the same problem occurs after cleaning, replace the drum
unit with a new one.
• The paper tray ground terminal located in the machine body may be
dirty. Clean the contact with a dry cloth.

Brother MFC-7840W 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)	22 ppm
Grayscale levels	256
Input color depth	24 bit
USB port	Yes
Standard interfaces	USB 2.0
USB 2.0 ports quantity	1
Dimensions (WxDxH)	428 x 396 x 304 mm
Networking features	10/100 Base-TX Ethernet
Wireless technology	IEEE802.11b/g
All-in-one functions	Copy, Fax, Scan
Color all-in-one functions	scan, n
Compatible operating systems	Windows Vista/XP-Home/2003/2000 Mac OS X 10.2.4 & later Linux printer driver
Copier resize	25 - 400 %
Maximum copy resolution	600 x 600 DPI
Maximum number of copies	99 copies
N-in-1 copy function (N=)	2, 4, 9, 16, 25
Copy speed (black, normal quality, A4)	22 cpm
Faxing	Mono faxing
Fax memory	500 pages
Fax coding methods	MH, MMR (Fax coding method), MR
Fax speed dialing (max numbers)	200
Maximum input capacity	250 sheets
Multi-Purpose tray input capacity	1 sheets
Auto document feeder (ADF) input capacity	35 sheets
Internal memory	32 MB
Sound power level (standby)	32 dB
Sound pressure level (printing)	53 dB
Media weight (tray 1)	60 - 105 g/m²
ISO A-series sizes (A0...A9)	A4, A5, A6
ISO B-series sizes (B0...B9)	B5, B6
Maximum ISO A-series paper size	A4
Multi-Purpose Tray media weight	60 - 163 g/m²
Supported network protocols (IPv4)	IPv4, IPv6
Sustainability certificates	ENERGY STAR
Power consumption (standby)	75 W
Power consumption (PowerSave)	12 W
Power consumption (average operating)	320 W
Package weight	13.400 g
Market positioning	Home & office