Horizontal Deflection Circuit; Horizontal Width Control - Nokia 447ZiPlus Service Manual

6-9. Horizontal Deflection Circuit

Q429 is switched by the horizontal drive signal from pin26 of I401 via level-shift components R424,
C427, and D428. This produces a sufficient voltage to drive T430, Snubber network R429, C429
compensates for leakage inductance in T430 and shapes the base drive waveform.
The drive signal is fed to Q433 via D431, R431. When Q433 is at the " off " state, the changes stored
on the base and collector of Q433 will discharge via D431.By this way, switching loss will be reduced.
The drive signal controls Q433 to switch on and off, so that saw-tooth waveform current through the
horizontal deflection coil is obtained.
The positive horizontal fly-back pulse signal taken from pin6 of T440 feedback to pin 12 of I401 via
R405, R408. This fly-back signal not only provides proper timing reference for horizontal drive output
but also supply necessary blanking for video output.
The basic deflection circuit comprises switching transistor Q433; transformer T440; damper diode
D435; tuning capacitors C434/C435; S correction capacitors C405/C472/C477 and linear coil
L483/L454. The frequency table is for CS function as shown on page 13.

6-10. Horizontal Width Control

The monitor uses a diode modulation circuit. For the control of width, it is achieved by changing
the base voltage of Q467. The control voltage (0V ...5V) is derived from pin2 of CPU I501 via
Q502, any change of DC voltage on the base of Q470 will vary the DC resistance between the
collector and emitter of Q470. Low DC resistance on Q470 will cause large width control current
flows into Q470 via L471 and then the horizontal width is increased.
6-11. Pincushion Control
Pincushion control signal is derived from pin24 of I401. This pincushion control signal is AC coupled
to the base of Q467 via C464 and divider R463/R464. Also this same pincushion control signal will
be amplified by Q466 and coupled via C404A to the collector of Q468,Q467,Q468 act as differential
amplifier. Output at base of Q470 modulation current flow in parabola shape, thus side pincushion is
corrected.
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