Brother HL-4000CN Service Manual page 90

1.3.7 Tertiary transfer (IDT 2 - paper)
In the tertiary transfer process, finished toner image formed on the IDT 2 surface is
transferred onto the paper under the voltage supplied to the transfer roll cartridge.
Transfer roll cartridge is composed in the transfer roll cartridge ASSY.
Transfer roll cartridge is a conductive roll and receives positive high current from
HVPS.
When paper passes through between IDT2 and transfer roll cartridge, plus potential
is given to the back side of the paper so that the toner on the IDT 2 is transferred
onto the paper. At this time, potential on the transfer roll cartridge is higher than that
on the IDT 2.
IDT1 surface
Yellow
toner image
Magenta
toner image
IDT1 surface
Cyan
toner image
Black
toner image
III-12
Fig.3-19
IDT2 surface
Yellow
toner image
Magenta
toner image
Cyan
toner image
Black
toner image