NEC MultiSync 75F-3 Service Manual page 76

Test Circuits
J1
RED OSD INPUT
GREEN OSD INPUT
BLUE OSD INPUT
OSD INPUT SELECT
RED VIDEO IN
GREEN VIDEO IN
BLUE VIDEO IN
V
CC
R11
100k
VIDEO CONTRAST
POT5
100K
C12
0.1 µ F
OSD CONTRAST
POT6
100K
FIGURE 2 LM1281 OSD Video Preamp Demonstration Board Schematic
C2
0.1 µ F
R1
1
R2
2
R3
3
R4
4
R6
C3
5
R5
50/75
6
C5
0.1 µ F
7
R7
C4
8
R8 33
50/75
9
C6 C7
100 µ F 0.1 µ F
10
R9 C9
11
R10
10 µ F
33
50/75
12
C8
0.1 µ F
13
C10
0.1 µ F
14
C11
0.1 µ F
V = + 12V
CC
C1
100 µ F
28
C21
0.1 µ F
27
C20
0.1 µ F
26
C19
0.1 µ F
25
C18
0.1 µ F
24
C17
0.1 µ F
23
LM1281
TOP VIEW
22
C15
0.1 µ F
21
20
19
C14
0.1 µ F
18
17
C13
0.1 µ F
16
R17
15
100
*L1 is a Ferrite Bead
73
R21 47k
RED DRIVE ADJ.
POT3
100K
GREEN DRIVE ADJ.
POT1
100K
BLUE DRIVE ADJ.
POT2
100K
RGB CUTOFF ADJ.
POT4
100K
L1
R19
RED VIDEO OUT**
R20
430
2.4k
C16
100 µ F
R18
GREEN VIDEO OUT**
R17
430
2.4k
R15
BLUE VIDEO OUT**
R16
430
2.4k
R17
BLANK GATE
100
CLAMP GATE
**50 Ω Termination to
be Used at Outputs
TL/H/12355-12