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This circuit has the function of auto degaussing and manual degaussing. When power supply is
switched ON it is auto degaussing stage. When user make the selection of the manual degaussing
function in OSD, the degaussing current will flow through coil to degauss the screen of monitor.
TR602 is a PTCR to control degaussing coil current
2.2.3.8 Power Saving Control
Mode
Normal
Stand-by
Suspend
Off
When both of the H-sync and V-sync are none, the power supply +6.3v and+15v output will be cut-
off. The power input will be under 5W. When the H-sync is none, the power supply +15v output will
be cut-off. The power input will be under 15W. When the V-sync is none, the power supply +6.3v
and+15v output will be cut-off. The power input will be under 5W.
2.2.4 Video C.K.T. Block Diagram
R OSD
G OSD
(FROM
IC 1901 )
B OSD
CUT
R
G
VIDEO
B
CONTRAST
(FROM IC801)
BEAN CURRENT
(FROM F.B.T.)
H-PULSE
(FROM F.B.T.)
2.2.4.1 OSD 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 two amplifiers. The first one, preamp CKT, process the signal and mix up the
OSD, and the second one does the power amplification.
(b) OSD preamp IC101, LM1279, will output the R.G.B signals seperately. The R.G.B driver will
control the gain of these three guns individually to approach the white balance of CRT.
(c) The signal H-Blank is to let the output of LM1279 down to 0.2V while non-display duration. Then
the CRT driver CKT will generate a level higher than Black Level. (i.e. SYNC TIP), therefore the
video signal will be blanked in order to prevent the fold over to occure while adjusting H-phase.
Besides, the SYNC TIP is used for the DC Restoration of cascode CKT.
(d) LM1279 is equipped with OSD mixer. when signal CUT is Low, the output of LM1279 is video
Circuit Operation Theory
H-sync
V-sync
Normal
Normal
None
Normal
Normal
None
None
None
DRIVE
(FROM IC1901)
B
G
R
PREAMP
CKT
LM1279
IC101
ABL CKT
Q322,323
H-BLANK
CKT
Q320
API Confidential
No Copy/Reproduction Allowed
LED
Green
Orange
Orange Flash
Orange Flash
BIAS
(FROM IC 1901)
B
R
G
DC RESTORE
Q111,112
Q131,132
Q151,152
CRT DRIVER
CKT
LM2407
IC102
BRIGHTNESS CKT: Q203
CHANGE MODE BLANK CKT:Q202
V BLANK CKT: Q202
SPOT KILLER CKT: Q202
Power Rating
100
15W
5W
5W
R
G
B
G1
2-11
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