CTX EX951F, Service Manual

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12
On Screen Display Controller
The IC804 is designed for display the built-in characters or fonts onto monitor screen. The display operation is by
transforming data and control information from micro controller to RAM through a serial data interface.
Pin 2 is used to control the internal oscillator frequency by DC voltage input from external low pass filter (R830,
C811, R833) and filter (R126, C115) is used to regulate the appropriate bias current for internal oscillator the
resonate at specific dot frequency.
Pin5 is input the horizontal fly back pulse, for PLL generator tracking.
Pin6 is left floating, I2C bus is enabled. Otherwise the SPI bus is enabled.
Pin7 the external data transfer through this pin to internal display registers and control registers
Pin8 the clock-input pin is used to synchronize the data transfer.
Pin10 is input the vertical flyback pulse for synchronizing the vertical position.
Pin12 is output a blanking signal to cut off external R.G.B signals of VGA while this chip is displaying characters
or windows.
Pin13, Pin14, Pin15 is used to output the OSD (B.G.R) video signal.
5-2 DEFLECTION CIRCUIT
The deflection circuit is achieved by a high performance and efficient solution IC 401 (UPC1888ECT) for this
monitor. The concept is fully DC controllable and can be used in applications with a micro-controller solutions.
The UPC1888ECT provides sync. Processing with full auto sync. capability, a flexible SMPS block and an
extensive set of geometry control facilities. Further the IC generates the drive waveforms for DC coupled vertical
boosters to the TDA9302H .
Horizontal Oscillator
The oscillator is of the relaxation type and requires a capacitor of 390nF C403 at pin 23. The maximum oscillator
frequency is determined by a resistor R443 from pin 22 to ground.
PLL2 Phase Detector
This phase detector compares the line flyback pulse at pin 18 with the oscillator saw-tooth voltage. The HFL0
detector thus compensates for the delay in the external H-deflection circuit by adjusting the phase of the HDRV
output pulses. The phase between H-flyback and H-sync can be controlled at pin21.
X-ray Protection
The X-ray protection input pin 19 provides a voltage detector with a precise threshold. If the voltage exceeds this
threshold for a certain time, an internal latch switches the whole IC into protection mode. In this mode several pins
are forced into defined states:
Pin17 (HDRV) is floating
Pin 12 (BDRV) is floating
Vertical Oscillator
The vertical free –running frequency is determined by the capacitor C604 at pin 2 and resistor R608 at pin20.
Usually the free-running frequency should be lower than the minimum trigger frequency.