Circuit Operation Theory
API Confidential
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2-3
According to the CRT spec
H dynamic focus Vpp = 300 V H dynamic focus Vpp = 130 V
2.1.4.1 Vertical Dynamic Focus
The signal from IC201 (pin 32) is a vertical frequency parabolic waveform.
Q321 : an inverting amplifier stage.
2.1.4.2 Horizontal Dynamic Focus
The wavefom of C313 (CS-2, CS-1) is a horizontal frequency parabolic waveform, and is amplified
by T304.
3
4
1
2
+
R379
C336
R327
T304
Q321
C328
C327
C329
R351
R352
R353
R354
1/4W
(OPEN)
(D)
500V
(OPEN)
1/2W
20
19.20113.011
BF423
(D)
500V
470P
50V
47U
(EL)
400V
0.022U
(MPP)
62K
2.4K
1/4W
620K
1/2W
20
+12V
CS-1
FOCUS
-190V
CS-2
DAF
Fig 4 Dynamic Focus circuit
2.1.5 Brightness & Spot Killer CKT
2.1.5.1 G1 CKT
The bright control signal from UC controller is about 0 ~ 5V, when the voltage of bright control signal
increases, the current flow through R241 increases and the voltage of G1 decreases.
2.1.5.2 Blanking CKT
To avoid the disturbed picture display on the screen, we have to blank the monitor in the following
situations.
(1) when display mode is changed.
(2) when the monitor enter the power saving mode.
(3) blank the vertical retrace line
When the "blank" signal becomes "high" Q202 "ON", Q203 "OFF".G1 voltage is about ( -190 *
R253/(R253+R241)) -184V. The signal which is IC201 (pin 16) is inverted and amplified by Q202,
and coupling to G1. During the vertical retrace interval , the G1 voltage will be drop down about
48V.
