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[7] High voltage unit
(MAIN
PWB)
7
!
ig ce
Fs Oe ae a eet Ee
ee
1. General Description
There are three types of corona units used in the SF-7200;
the main, transfer, and separation corona units.
The main corona applies a uniform negative charge to the
drum surface. The transfer corona is used to transfer the
toner from the drum
onto the copy paper. The discharge
corona
reduces the negative charge on the drum to allow
easier toner removal at the cleaner unit.
A fault sensing circuit has been incorporated in the transfer
high voltage unit to prevent developer pull. Copier opera-
tion is stopped by the activation of the status code function
"C2",
if the machine
experiences a loss of transfer high
voltage.
For example: When the corona wire is broken or when the
corona is not properly inserted.
2. High Voltage Units
(1) Main high voltage unit (MHVG)
output=—6.38K
VDC, 580uA
(2) Transfer high voltage unit (THVG)
output=—6.16K VDC, 280uA
(DCD
sheet
current:
—20+3uA,
with
tolerance
of Q2uA
between the front and the rear)
SF-7200
Main corona
Discharge corona
Transfer corona
(3) Discharge high voltage unit (DHVG)
output=+5.07KVDC, 118uA
(DCD
sheet
current:
+4.0+1uA,
with
tolerance
of 1A
between the front and the rear)
3. Corona Wire Replacement
Refer to the figure below for replacement of the corona
wire.
(1) Main corona wire
Corona wire
Cc
——
jon
aC
5
TD
| ar
> c
ie
—
u
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