F770D Technical Service Manual
4. Horizontal Deflection
TDA9116 is an I2C autosync deflection controller for H/V sync and drive processing.
All functions are controlled by I2C bus.
When H-Sync is applied, the internal oscillator is automatically locked.
The duty-cycle of H-output pulse Pin 26 is variable by frequency.
QH08 and TH01 are used to drive the H-output transistor (QH09). QH09 is turned on, it
conducts current through the deflection yoke on the right hand side of the screen.
This current comes from the S correction capacitors (CH27, CH29, CH32, CH34), which have
a charge equal to the effective supply voltage.
When the QH09 is opened up, the damper diode(DH12) allows current for left hand side of
the screen to flow back through the deflection yoke to the S capacitors.
The flyback capacitor (CH23) determines the size and length of the flyback pulse.
The S capacitors correct outside versus center linearity in horizontal scan.
Three FETs (QH11, QH12, QH13) select the value of S capacitors.
H-centering is controlled by a switch(SWH01). The switch selects DC offset current flow
through the yoke.
A diode modulator is used to control the E-W correction and H-size. ICH01 generates the
E-W parabora wave using vertical amp.
A power buffer (QH02, QH03) drives the diode modulator.
In order to keep the high voltage constant independent of the horizontal scan frequency, the
supply voltage of FBT must increase with increasing scan frequency proportionally. A step-
up mode DC-DC converter with PWM is used to realize this demand.
ICH01 compares high-voltage feedback with reference voltage. Its output pulse switches a
FET(QH07). To adjust the high voltage, TDA9116(ICH01) has a control terminal (Pin14).
5. Vertical Deflection
In vertical section of TDA9116 there is auto-sync processing.
The vertical output stage consists of a power OP-AMP with extra flyback generator.
TDA9302H(ICV01) is used as vertical output stage.
6. X-Ray Protection and Beam Current Limiting.
A failure in the horizontal scan control section could cause a dangerous situation; the high
voltage might rise to an unacceptable high level. When the flyback voltage rise to
unacceptable level, the (Pin25) of ICH01 detects these states over 8.0V
It causes the H-drive stage and oscillator to be turned off. Then high voltage is shut down
until the power switch is on.
The average anode current is measured at lower side of the High Voltage winding of the
FBT. ABL flows through Connectors(CNC04,CNC01) connected ICC01(LM1267) and through
RM07 Connected ICM01 Pin39. and ABL is controlled by ICM01.
7. Video Amplifier and OSD Interface
LM1267(ICC01) is a Very High Freguncy video amplifier with three matched video
amplifiers, OSD Contrast Control SDA, SCL,OSD Interface, OSD BLK drive controls, blanking
gate and clamp gate. H-blank signal is applied to Pin 24. During blanking all three outputs
are thrown to the pedestal level. MCU(ICM01)Pin32 Clamp is used to a clamp signal.
The signal is applied to ICC01 Pin 23.
Three OSD inputs (Pin 1,2,3 of ICC01) are TTL compatible and typical bandwidth is 80MHz.
A fast commutate pin is provided to select either the video or the OSD inputs as a source
for amplification.
gain of three internal variable gain amplifiers through the I2C bus interface. MTV 021 is
designed for monitor application to display built-in characters or fonts on to monitor
screen.
The display operation occurs by transferring data and control information from the MCU to
RAM through a serial data interface.
The output stage is made of 3-channel power amplifier (LM2467, ICC03 ). The output is
capable of 40 Volts swing in less than 9 nsec
The three cathodes are AC coupled to the video amplifiers. The DC level on each cathode is
set by a cut-off amplifier and clamp diode. The value of the DC voltage is adjusted by DACS.
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