Toshiba TW40F80 User Manual download pdf (Page 46)

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4. CIRCUIT OPERATION

4-1. Video/Color/Deflection Process Section

The video/color/deflection section is shown in Fig. 6-2.

The luminance signal is supplied from pin Y08 of PY01 and

its frequency bandwidth is limited by the low pass filter (LPF)

and then input to pin 36 of V/C/D IC (VIDEO IN). The Y

signal output from pin 12 of PY01 superimposes the charac-

ter signal on the video signal by QY49 and QY44, and then

output to the sub screen process section.

QY49 and QY44 work as the analog switches. When the

screen is displayed in DW, the switch operation is not car-

ried out and the same signal as the input signal is output, and

when the 9-screen multi-search process is carried out, the

switch operation is carried out.

The OSD signal superimposes the shade of character signal

by QY49 and the character signal by QY44 on Y signal.

On the other hand, the color signal is supplied from pin Y15

of PY01, limited its frequency bandwidth by the band pass

filter (BPF) and then input to pin 34 of QY01 (COLOR IN).

The color difference signals of the demodulated signal (R –

Y) and ( B – Y) are output from pins 13 and 14 of QY01. In

the same way as the Y signal, the (R – Y) and (B – Y) signals

are superimposed on the character signal with OSD signal

by QY44.

The GBR matrix circuit which converts the Y, R – Y and B –

Y signals into three primary color signal of G, B and R is

used to convert the (R – Y) and (B – Y) signals into I and Q

signals.

In the GBR matrix circuit, each G, B and R output is output

as G – Y, B – Y and R signals when the Y signal is not input.

Then the B – Y signal is converted to Q signal, R – Y to I

signal pseudically by turning the phase by an angle of 33°.

Thus, R – Y and B – Y signals are input to pins 18 and 19 of

QY01, and the output signals from pins 23 and 24 are devel-

oped as the I and Q converted signals pseudically. The am-

plitude of the signals is amplified by 6 dB amplifier of QY23

and the signals are output to the sub screen process section.

Since the sync signal is added to the luminance signal, the

signal is input to pin 39 of QY01 (SYNC SEP IN) and the

sync signals of HD and VD are output to pins 10 and 11 of

QY01. The HD signal is waveshaped by QY42.

The HD signal (WHD1, WHD2) is used as the horizontal

pulse for sub screen write and the VD signal (WVD) is as the

vertical pulse for sub screen write in the sub screen process

section.

In the sub screen microcomputer section, various kinds of

control signals (brightness, density, hue, etc.) are output from

the sub screen control microprocessor QY91 and the signals

are used for the level matching adjustment. So the setting for

the sub screen cannot be made by the user. Furthermore, the

OSD signal for OSD superimposing is output.

The sub screen process IC control program is stored in the

nonvolatile memory of the sub screen control microproces-

sor QY91 in order to control the sub screen process IC

(TC9092AF), and the data is sent via I

C bus.

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