Philips 107T60 Service Manual page 54

54
107T6 CRT
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HORIZONTAL DEFLECTION / VERTICAL DEFLECTION / EHT GENERATOR
HORIZONTAL DEFLECTION
The heart of horizontal/vertical deflection controller is Demic IC - SAA4848, which can offer a complete and
efficient small signal sync processing for auto-sync monitors. All functions are controlled via I2C bus.
This controller provides sync processing, which can accept separate and composite (H+V) input signals. A
very short settling time after mode change for protection of external power components has been taken into
account. However, it should be noted that according to V32 107T6 spec this monitor doesn't support
composite (H+V) input signals to avoid some troubles.
The SAA4848 provides extensive functions like a flexible B+ controller block of H-deflection and a geometry
control with facility, leading to excellent picture quality. This device also can directly drive the vertical
deflection output stage. The line driver stage, the E/W output stage and all controls are tracked with the
incoming frequencies. Picture can be adjusted along horizontal/vertical direction by OSD H-shift/V-shift
control. The horizontal size, east/west, trapezoid corrections can be adjusted by the output of pin35 (EWout),
which is led to the diode modulation circuit. S-capacitors plus power MOSFET switches and DC controlled
linearity coil are designed for optimal picture linearity.
VERTICAL DEFLECTION:
The majority of vertical deflection function is integrated by two ICs : SAA4848 and TDA4863.
The SAA4848 takes care of sync polarity correction, automatic catching and holding of the vertical oscillator,
generation of saw-tooth drive current for vertical output and vertical s-correction, and generation of a correct
V-blanking pulse for video blanking during vertical retrace time.
The TDA4863 is a DC-coupled vertical deflection booster with differential input signals, suitable for color
monitors. The output stage has thermal and soar protection, and high linear saw-tooth signal amplification to
obtain the required vertical deflection current. The voltage supply at flyback time for output stage is generated
by the internal flyback generator and the external diode (6401) and capacitor (2405) which make the so-called
pump-up circuit.
EHT GENERATOR
The IC SAA4848 is also used as a controller to generate required extra high voltage for CRT via a
converter (7615) which supplies the required B+ to LOT's primary. This is a conventional combination circuit
of horizontal deflection and EHT generation.
Flyback transformer (LOT) transfers the primary voltage to the required anode voltage and rest tertiary output
voltages. The adjustable focus (G3) and screen (G2) voltages are internally derived from the anode voltage.
Another secondary winding is used to generate the voltage for G1. Dynamic focus on G4 is derived from a
DAF transformer (5671) to get a good focus performance. (G4 is also adjustable in factory mode).
For safety reasons, x-ray protection circuit is included, that SAA4848 will shut down EHT generator and
horizontal deflection if the anode voltage exceeds a certain value (27-29kV).
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VIDEO AMPLIFIER & DDC2B
VIDEO AMPLIFIER:
The video circuit mainly consists of LightFrame IC TDA4823, pre-amplifier NT6812, post amplifier STV9556
and DC restoration IC LM2480. The video DC level and gain at cathode are controlled via I2C bus & software.
When Lightframe IC is enabled by pressing the LF key, RGB input signals will be amplified with an extra
amplification factor up to 1.4.
2004-04-19
BRIEF CIRCUIT DESCRIPTION
:
1 inch Monitor
7 CRT
TYPE :107T60/00
BRAND : PHILIPS
2004-04-19
8639 000 15483
3
4
buck