Xerox WorkCentre Pro 412, Service Manual

Page: 58 / 192

Circuit Description
WorkCentre Pro 412
Launch Issue
5-32
August 2001
5-5-7-6. THV(THV(+)/THV(-) Output Unit)
Tr) output unit is the transfer output control signal ’PWM-LOW ACTIVE’.
When THV-PWM LOW signal is received, Q203 turns on and the steady voltage will be accepted to the non-
inverting terminal of OP-AMP 324. As the voltage is higher than the inverting reference voltage of OP-AMP,
OP-AMP output turns high.
The 24V power adjusts the electric potential to ZD201 and ZD202, sends IB to TRANS auxiliary wire through
current-restricting resistance R215 via R212 and C204, and eventually Q204 will turn on. When the current is
accepted to Q402, Ic increases to the current proportional to time through the T201 primary coil, and when it
reaches the Hfe limit of Q204, it will not retain the “on” state, but will turn to “off”. As Q402 turns 'off', TRANS
N1 will have counter-electromotive force, discharge energy to the secondary coil, sends current to the load
and outputs THV voltage through the high voltage output enable, which is comprised of Regulation– circuit.
The output voltage is determined by the DUTY width. Q203 switches with PWM DUTY cycle to fluctuate the
output by fluctuating the OP-AMP non-inverting end VREF electric potential, and the
maximum is output at 0% and the minimum, at 100%.Transfer(-) output unit is THV-EA 'L' enable.
When THV-EA is 'L', Q302 turns on and the VCE electric potential of Q302 will be formed and sends IB to
TRANS auxiliary wire through R311, C305 and VR302 via current-restricting resistance R314, and eventually
Q303 will turn on. When the current is accepted to Q303, Q303's Ic increases to the current proportional to
time through the T301 primary coil, and when it reaches the Hfe limit of Q303, it will not retain the “on” state,
but will turn to “off”. As Q303 turns 'off', TRANS N1 will have counter-electromotive force, discharge energy to
the secondary coil, send current to load and output THV(-) voltage through the high voltage output enable,
which is comprised of Regulation circuit.
#7 TEV-PWM
5V
U2
1 2 3
R201
10K
U2
R205
1.8K
R206
100
Q203
A708Y
R208
30K
18V
R209
100KF
VR201
50K
R207
2K
C201
103 C202
121
R210
845KF
D202
1N4148
R211
1MF
5
6
7
+
_
U1
11 KA324 24VS
+
C101
35V47
U
F
D201
1N4148
24VS
R213
2.2K
R212
680K C203
472 D203
1N4148
ZD201
5.65V ZD202
705V R214
2.2K
C204
333Z
Q204
D526
T201
KAB-007
C206
6KV470pF
C205
2KV68pF D204
6KV
D206
6KV
C209
6KV
C208
6KV
D205
6KV D207
6KV
R215
390
C207
3KV470pF
R216
SBR306 R218
MGR1/2W100KF
R217
SBR207
#17
#19
#5
#24
5V
TEV-EA
TEV-READ
5V
D301
1N4148
5 6
7
U2
7407
D-GND
24VS
C4
103
8
9
10
U1
+
_
KA324
R301
470K
C301
222
R302
33K R303
100KF
C302
102
D302
1N4148
C303
103
R304
389KF
R305
10KF
VR301
5K
R306
26.1KF
C304
500V103Z
18V
R309
202K
R307
33K
Q301
A708Y
18V
R310
2.2K
R308
33K
Q302
A708Y
R312
1W56
R313
1W56
Q303
D526
R311
100KF
C305
333Z
VR302
2K
R314
1.7K
KAB-006
T301
1
5
2
4
6
7
1
5
2
4
7
6
C307
3KW470pF D304
4KV
C306
2KV68pF
D303
4KV
C308
3KV470pF R315
SBR306