Circuit Description; Micro Controller Circuit; Deflection Circuit - HP MX704 Series Service Manual

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
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. Pin39/Pin40 are for the H-SYNC and V-
SYNC input, Pin32/Pin33 will output the same signal as input sync signal without delay, and the polarity are
setting in the positive. When no signal input, the Pin32 will output a 72Hz V-SYNC free run signal. The Pin33
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 IC 401 (STV6888) for this
monitor. The concept is fully DC controllable and can be used in applications with a micro-controller solutions.
The STV6888 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.

5. CIRCUIT DESCRIPTION

13
base timer, internal H-sync