Acer V551 (new) CRT Monitor Service Guide
Chapter 2 Circuit Operation Theory
9
Confidence and Property
2. Video CKT
(1) Black Diagram of Video
Preamp CKT
MM1375XD
IC101
Cascode CKT
Q101,110
Q103,111
Q105,112
ABL CKT
Q316
Clamp CKT
Q 205
CONTRAST
(From uC IC801)
Beam Current
(From FBT)
DC Restore
CKT
H-clamp
(From IC201)
R
G
B
G1
Brightness CKT: Q203
Change Mode Blanking:Q202
V-blanking CKT: Q201
Spot Killer CKT: Q202
R
G
B
VIDEO
(From PC)
(2) MM1375XD Block Diagram
The function block below represents one of the threevideo amplifiers in the MM1375XD
along with the contrast, gain adjust and brightness contrals. The Contrast Control is DC-Level
(0 ~ 4 V) operate attenuator which controls the video gains of the three channels (R, G, B)
simultaneously The Gain
Adjust Control, which is also a DC-level operated circuit, provides a 6 dB gain adjustment to
each channel. During the retrace period, the Clamp Comparator will charge or discharge the
clamp capacitor by comparing the external brightness (clamp+) level with the video output DC
level thus that the brightness level is maintained.