Compaq MV7540, Service Manual

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HP MV7540
13
5. Circuit Description
5-1 Micro Controller Circuit
MICRO Controller
The IC101 contains a 6502/8051 8-bit CPU core, 512 bytes of RAM, 16K bytes of ROM,14 channel 8 bit
PWM D/A converters, 2 channel A/D converters for key detection, one 8 bit pre-loadable base timer, internal
H-sync and V-sync signals processor providing mode detection, watch- dog timer preventing system from
abnormal operation, and an
I²C bus interface.
H/V sync signals processor
The functions of the sync processor include polarity detection, H-SYNC & V-SYNC signals counting,
Programmable SYNC signals output, free running signal generator. Pin41/Pin42 are for the H-SYNC and V-
SYNC input, Pin33/Pin34 will output the same signal as input sync signal without delay, and the polarity are
setting in the positive. When no signal input, the Pin33 will output a 72Hz V-SYNC free run signal. The Pin34
will output a 48KHz H-SYNC free run signal. for the monitor testing use.
5-2 Deflection Circuit
The deflection circuit is achieved by a high performance and efficient solution IC401 (STV9118) for this
monitor. The concept is fully DC controllable and can be used in applications with a micro-controller solutions.
The STV9118 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 TDA9302A.
Horizontal Oscillator
The oscillator is of the relaxation type and requires a capacitor of C409 at pin6. The free running frequency is
determined by a resistor R412 from pin8 to ground.
PLL 1 Phase Detector
The phase detector is a standard one using switched current sources. It compares the middle of H-sync. with
a fixed point on the oscillator saw-tooth voltage. The PLL loop filter C435, C437, R411 is connected to Pin9.
PLL2 Phase Detector
This phase detector is similar to the PLL1 detector and compares the line flyback pulse at pin 12 with the
oscillator saw-tooth voltage. The PLL2 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 pin5.
X-ray Protection
The X-ray protection input pin25 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:
Pin28 (BDRV) is floating
Pin26 (HDRV) is floating
Vertical Oscillator
The vertical free
–
running frequency is determined by the capacitance C613 at pin22. Usually the free-running
frequency should be lower than the minimum trigger frequency.