19
Explanation for circuit operation
3-3 Organization of deflecting part
This smoothing part is designed to deflect a 55” CRT Projection TV and correct a screen. The
design specifications of this deflecting part are as follows.
1) Working frequency: Horizontal frequency (31.45KHz, 33.75KHz). Vertical frequency
(60Hz)
2) Vertical / Horizontal deflection
This deflection IC used in this deflecting part is TDA4856, the latest HC Control IC of
PHILPS. Co. Ltd. The main functions of this IC are shown below.
a. All functions concerned with vertical and horizontal deflection can be adjusted by HC
control of U-COM.
b. The geometrical correcting part such as V-S linearity, VC linearity, trapezoid, Side-pin W-
S, parallelogram and Side-pin balance are includes in the IC.
c. Twenty built-in D/A converter channels are adjustable respectively.
d. A vertical S-C correcting circuit is built in.
e. The amplitude and phase of a horizontal dynamic focus linked with horizontal size can be
adjusted.
f. A vertical dynamic focus circuit linked with vertical size is included.
g. A horizontal moire canceller circuit is built in.
h. A Sync On Green circuit is built in.
i. Vertical / Horizontal size can be controlled.
j. Vertical /Horizontal position can be controlled.
k. Vertical /Horizontal Sync of bipolarity can be input.
l. A vertical blanking generating and video clamp generating circuit are included. (Sand
castle output)
m. A vertical waveform of bipolarity is output.
n. A horizontal lock detecting circuit is included.
o. Low jitter
3-4 Explanation for operation
1) Vertical / Horizontal deflection IC circuit part
HD and VD signal supplied via connector PA402 in A/V board is input to H-in (Pin No.15)
and V-in (Pin No.14) of deflection IC as Sync. The input Sync goes through an internal Sync
processor and is output as H Drive to H-out (Pin No.8).
At this time, the internally processed Sync isn’t affected by polarity and for H Sync, a
composite signal can be input. For H-OUT, the duty can be selected and controlled to 40,
50, 60% (+/- 3%) by I
2
C control. Free Run frequency at No Sync can be adjusted by I
2
C
control. Dividing a collector pulse from horizontal deflection, an internal PLL is taken after
FBP (Pin No.1) input and the phase is adjusted to horizontal Sync.
In this IC, all geometrical compensating waveforms related to horizontal are output from E/W
(Pin No.11), supplied for a horizontal B+ generator in a horizontal drive part, added to a
horizontal B+ waveform in the form of parabola and provided for D1 of horizontal output TR
(Q402). The horizontal dynamic focus signal from this IC is first amplified via an amplification
part (IF 11).
2) Horizontal drive part
This horizontal drive part consists of horizontal B+ supply part and horizontal output part.
