Samsung SF-830 Service Manual page 154

3-5-7-4 MHV (Electrification Output Enable)
Electrification Output Enable is the electrification output control signal 'PWM-LOW ACTIVE'.
When MHV-PWM LOW signal is received, Q401 turns on and the steady voltage will be accepted to the non-inverting ter-
minal of OP-AMP 324. As the voltage higher than the inverting reference voltage of OP-AMP, which is set to R405 and
R406, OP-AMP output turns high. This output sends IB to the TRANS auxiliary wire through current-restricting resis-
tance Q402 via R408 and C403 and Q402 turns on. When the current is accepted to Q402, Ic increases to the current pro-
portional to time through the T401 primary coil, and when it reaches the Hfe limit of Q402, 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 sec-
ondary unit, sends current to the load and outputs MHV voltage through the high voltage output enable, which is com-
prised of Regulation– circuit.
U103 7407
MHV-PWM
R412 2.2K
3-5-7-5 BIAS (supply/dev/blade output unit)
BIAS (Electrification Output Enable)Electrification Output Enable is the electrification output control signal 'PWM-LOW
ACTIVE'.When BIAS-PWM LOW signal is received, Q501 turns on and the steady voltage will be accepted to the non-invert-
ing terminal of OP-AMP 324. As the voltage higher than the inverting reference voltage of OP-AMP, which is set to R506
and R507, OP-AMP output turns high. This output sends IB to the TRANS auxiliary wire through current-restricting
resistance Q502 via R509 and C504 and Q502 turns on. When the current is accepted to Q502, Ic increases to the cur-
rent proportional to time through the T201 primary coil, and when it reaches the Hfe limit of Q502, it will not retain the "on"
state, but will turn to "off". As Q502 turns 'off', TRANS N1 will have counter-electromotive force, discharge energy
to the secondary unit, sends current to the load and outputs DEV voltage through the high voltage output enable, which
is comprised of Regulation-circuit.
5V
R520
R501
26K
Q501
100
BIAS-PWM
A708-Y
2
CON03-#24
U103-A
R519
7407
2.2K
R503
100KF
R502
2K
Samsung Electronics
18V
R405 220K
Q401 A708
R403 130K +
R404
27K
R402
_
82K
C407
R411 2K
104
R406
2.2K
C503 R508
104 47K
R506
86.6KF
5
_
7
U1
+
R509
6
47K
U101-B
C501
R504
KA324
104
56.6KF
C502
R507
222
12KF
T401
24VS
Q402
D526
24VS
R408 R409
47K 390
KA324
C403
333
24VS
D502
T201
4KV
KAB-007
7
1
Q502 5 6
D526-Y
C505
2
2KV 680
4
R510
430
C504
R511
333
1W 3
CIRCUIT DESCRIPTION
MHV OUTPUT
C404
3K/471
D402 C406
3K/471
4KV
R416 R413
15M 12M
OPC
R417
15M
ZD401
150V
R514
MGR1/2W 50K
C506 ZD501
R515
3KV 471 100V
MGR1/2W 50K
ZD501
100V
R512
MGR1/2W 12MF
R516
MGR1/2W 50K
Repair Manual
BLADE
SUPPLY
DEV
3-35