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Video Output
Video Drive Circuit
R,G,B R,G,B R,G,B
Circuit CRT
Q341, Q342, Q343, Q344
MC13281 (IC301)
PC
Q351, Q352, Q353, Q354
Q361, Q362, Q363, Q364
Focus
BLOCK DIAGRAM
2nd Rectifier
Circuit
Screen
Micro processor Circuit Vertical Output
PC68HC705BD7 Circuit Anode
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Transformer (IC401) TDA4866 (IC601)
(T901) Mode Control
(
DPMS
)
V
Primary
Switching
Rectifier
Control
Circuit
Circuit
STR5717
( IC901) Horizontal/Vertical H High Voltage
Drive Circuit Generation
TDA4858 (IC701) Circuit
E
D/D CONVERTER
L N
AC INPUT
DESCRIPTION OF BLOCK DIAGRAM
1. Primary Rectifier Circuit 7. Horizontal and Vertical Drive Circuit
This circuit transform AC line voltage to DC voltage as This circuit take function, that are H/V-position, side-
the supplied source for secondary circuit. pincushion, and H/V-hold, with the output of
It is operated by C908 (electrolytic capacitor) and microprocessor circuit.
D901 (bridge diode). The generated vertical signal is applied to the vertical
output circuit. The generated horizontal signal is
2. Switching Control Circuit applied to the horizontal output and high voltage
generation circuit.
This circuit operate to be kept output of the second These are controlled by the IC701 (TDA4858) circuit.
rectified circuit in constant level any conditions; no
load, full load, line voltage variation, etc.
8. Vertical Output Circuit
The main function is operated by the IC901 (STR5717)
syncronizing to horizontal frequency via a connector This circuit take the vertical ramp wave from the IC701
that tie around the core of the T701 (FBT). (TDA4858) and perform vertical deflection by
supplying the saw-tooth wave current from IC601
3. Second Rectifier Circuit (TDA4866) to the vertical deflection yoke.
This circuit rectifying the pulse waveform of the
9. High Voltage Generation Circuit
transformer generated by switching control circuit.
It is consists of capacitors and diodes. This circuit used for generating pulse wave the primary
The output voltages are 77V, 65V, 39V, 12V, and 6.3V coil of T701 (FBT).
that are nacessary to the secondary circuit. A boosted voltage about 24kV appears at the
secondary of T701 (FBT) and it is supplied to the
4. Video Pre-Amp Circuit anode of the CDT (Cathode Display Tube).
This circuit pre-amplify the video signal (Red, Green 10. Blanking and Brightness Control Circuit.
and Blue) to make sufficient signal for the video output
circuit. Blanking circuit eliminate the retrace line by supplying
The function is operated by IC301 (MC13281). negative pulse to the G1 of the CDT (Cathode Display
Tube).
Brightness circuit is used for control screen brightness
5. Video Output Circuit
by changing the DC level of the G1.
This circuit amplify the pre-amplified signal and drive
the CDT (Cathode Display Tube). 11. D/D Converter.
The cascode amplify stages of each color are used to
this signal and the drive transister of cathode amplifier To obtain constant high voltage, this circuit supplies
lies inside of the IC301(TDA4881/2). controlled DC voltage to the FBT and the horizontal
The buffer stages are consists of PNP and NPN type deflection circuit according to the horizontal sync
transistors. frequency.
6. Microprocessor Circuit
This circuit generate control signal that need to
operating of horizontal and vertical drive circuit,
DDC1/2B (Plug & play), and DPM (energy saviing)
funtion. DDC1/2B (plug & play) function is operated
by combination of H/V Sync and SDA/SCL signal.
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