Power Supply Circuit - NEC MultiSync 4FGe Service Manual

CIRCUIT DESCRIPTION

1. Power Supply Circuit

+150V K1
+8OV
K2
K 3
+24V
Gr oundl
F
(A) +120V V 3
BRIGHTNESS
(B) - 6 0 V 3
SUB-BIAS CONTROL
(C) +80V V 3
VIDEO OUTPUT AMPLIFIER
(D) +12V V 3
D/A STARTUP CIRCUITS AND BRIGHTNESS/CONTRAST CONTROL D/A
SUPPLY VOLTAGE
(E) +12V V 3
HORIZONTAL OSCILLATION UNIT and POWER INDICATOR LED's
(F) +12V V 3
VIDEO BOARD OP-AMP SUPPLY, VIDEO PRE-AMPLIFIER SUPPLY, and VERTICAL
DEFLECTION OUTPUT SUPPLY
(G) +6V 3
CRT HEATER, and LOW +B PROTECTOR VOLTAGE
(H) +5V 3
CPU, E'PROM, and MULTIPLIER. D/A IC SUPPLY VOLTAGE
(I) - l o v 3
DISTORTION ADJUST UNIT.
(J) - 5 V 3
ANALOG MASTER OP-AMP and D/A OP-AMP OUTPUT SUPPLY VOLTAGE
(K) +18V V 3
DISTORTION ADJUST UNIT, and ANALOG MASTER SUPPLY VOLTAGE, and H OSC UNIT
(L) +24V 3
VERTICAL DEF
PROTECTOR UNIT, DISTORTION ADJUST UNIT and ANALOG MASTER SUPPLY VOLTAGE
Dropper Circuit t
+120V
H D e f l e c t i o n
.
High Voltage
DC/DC
Converter
I
l
tl2V Ser i es
R e g u l a t o r
+12V
S e r i e s
R e g u l a t o r
Low Voltage
C h o p p e r C i r c u i t
_
1
+18V S e r i e s
R e g u l a t o r
I
I
(Fig l-l) BLOCK DIAGRAM of the 4FGe's Power Supply
AND CUT-OFF CONTROL
C T ON
L E I S U P P L Y
F B T
+12V S e r i e s _
R e g u l a t o r
- t5V
1
1
H O R I Z O N T A L
, OSCILLATION UNIT
35
(A)
Hor
D e f l e c t i o n
- 6 0 V
(B)
+8OV ( C )
c
. +12V (D)
. +12v (F)
+6V (G)
S e r i e s + +5V ( H )
Regu ator
I
* +18V (K)
+ +24V (L)
and
OP-AMP
G
HI H V O L T A
IC
GE