Acer V551 (new) CRT Monitor Service Guide
Chapter 2 Circuit Operation Theory
10
Confidence and Property
(3) Preamp CKT
(a) AS shown in the block diagram:
The R/G/B signals will generate an enough amplitude of Vpp to show up on the CRT
screen after the amplification of the amplifiers.
(b) The purpose of signal CLAMP is to fix the black level of all R.G.B signals to the same
level after the AC couple. This is the DC Restoration of pre-amplify
(c) To fix Pin 1,19,20 voltage is to stabilize Pin 13,15,18 (R,G,B Output) DC voltage.
It’s purpose is to lower the Temp. of IC and transistors of Casecode CKT.
(d) VR104,105 control R.,G O/P gains
B OUT
B CUTOFF
B DRIVE
R DRIVE
R CUTOFF
R OUT
R CLAMP
R-IN
B CLAMP
B-IN
CLAMP
BLANK
CONT
G DRIVE
VCC1
G CUTOFF
G OUT
G CLAMP
GND
GND
VCC2
G-IN
22
21
15
16
17
18
19
20
14
13
12
8
7
6
5
4
3
2
1
11
10
9
+
+
+
6
5
4
3
2
1
D115
D113
D111
D112
D114
D116
C109
C110
IC101
C105
C103
C101
C118
C130
C122
ZD107
R109
R101
R102
R103
R142
R110
R112
R111
R138
R137
R108
R117
R123
R131
M102
R120
C106
C102
C104
C129
C154
C108
VR105
VR104
R106
R176
R177
R178
R100
D100
C100
1N4148
1N4148
1N4148
1N4148
1N4148
1N4148
(OPEN)
50V
(D)
0.01U
50V
(D)
MM1375XD
50V
0.1U
(D)
50V
0.1U
(D)
50V
0.1U
(D)
25V
47U
(EL)
50V
10U
(EL)
10U
50V
(EL)
8.2V
1/2W
120
75
75
75
1.5k
3k
3K
4.7K
9.1K
56K
100
390
390
390
20.60010.106
6P
1/4W
4.7
50V
0.1U
(D)
50V
0.1U
(D)
50V
0.1U
(D)
50V
0.01U
(D)
50V
(OPEN)
(D)
50V
0.01U
(D)
(B-DRV)
2K
(R-DRV)
2K
1/2W
100
33
33
33
4.7K
1N4148
(OPEN)
50V
(D)
GO
CONTRAST
+12V
CLAMP
+8V
+8V
+8V
+8V
RO
BO
RI
RI
GI
GI
BI
BI
H-BLANK