Video Circuit; Selection Of Bnc/D-Sub Input - NEC MultiSync FP1350 Service Manual

1. VIDEO CIRCUIT

1) Selection of BNC/D-SUB Input

The input selection circuit selects the BNC input or D-SUB input according to the voltage of IC731 pin19 (0V
or 5V). IC731 pin19 voltage changes whenever SW108(momentary switch) is pressed.
CPU detects BNC input or D-SUB input by input signal of Sync On Green and H/C sync. JC-1946UMW's
user can know by OSM information whether input is BNC or D-SUB. Sync sensor outputs high level when
fH is 1kHz or more, and low level when fH is less than 1kHz.
CPU detects BNC/D-SUB inputs and memories CONTRAST, SHARPNESS and EDGELOCK condition at
each input.
BNC
LC761G
G
LC763
H/C
D-SUB
LC762G
2
G
18
H/C
LC765
+5V
R7GP
C7GH
G
R7GR
+5V
R7G6
H/C
C7GJ
C702G
C701G
SYNC
R701G R701G
SENSOR
R709 C705
C704G
C703G
SYNC
R703G R704G
SENSOR
R70E C707
(Fig 1.1.1) Input Selection Circuit (Green channel)
R7GY
Q7G4
R7GT
R7GX
Q7G5
C7GG
R7GW
R7G8
R7G9
Q7G6
D7GF
(Fig 1.1.2) Sync Sensor (D-SUB part)
R73WG
IC731
4
M52755SP
R73XG
WIDE BAND
13 ANALOG
SWITCH
IC801
1
CPU
2
R7G2
MD7GG
R7G7
8-3
R736G
To
30
Amplification
Section
R73A
19
C73E
SW108
7
D/BNC
+5V
27
MRC802
C7G3
15 14
IC7G1
R7G4
HD74HC123AFP
2 13
MONOSTABLE
C7G6
MULTIVIBRATOR
To
CPU