Acer V551 (new) CRT Monitor Service Guide
Chapter 2 Circuit Operation Theory
4
Confidence and Property
(4) H-size control circuit
(a) H-size control voltage 0~5V input from "H-SIZE" net.
(b) Q301 is a buffer to separate prior signal and latter.
(c) R328 and D314 series connect to SC1 is used to compensating H-size by different
horizontal frequency (for VGA). The SC0, SC1 status are as follows:
(d) Horizontal size module merge the side-pin compensation waveform coming from Q312
then through Q307 inverting-amplify the modulating wave to control Q302
、
Q303
Darlington pair to control H-size.
(e) R307 and R308 separate the voltage B+ then provide the different voltage for different
horizontal frequency to H-size modulation circuit.
Fh SC0
SC1
>=45KHz 1
1
40K ~ 45K
1
0
45 ~ 40KHz
0
1
<35KHz 0
0
Cs truth table
+
C320
D314
D318
R328
R327
R305
D321
Q301
Q312
Q307
R345
R346
R301
R344
R307
R302
R312
R308
Q302
L303
Q303
D315
C316
R334
VR302
R358
D319
50V
1U
(EL)
1N4148
1N4148
150K
100K
33K
1N4148
H945
H945
H945
10K
8.2K
7.5K
18K
1/4W
300K
(FS)
1/2W
(SHORT)
3.3K
120K
(1%)
A733
19.40108.011
D669A
1N4148
50V
3.3U
(BP)
22K
(H-SIZE ADJ)
(SHORT)
(OPEN)
(OPEN)
VM
B+
+5V
EWDRV
+12V
+12V
SC1
SC2
H-SIZE
SC0