77
CIRCUIT DESCRIPTION
Chroma After Flex Converter Block Diagram Explanation
U205 - Flex Converter
Receives Main R-Y/B-Y/Y from I205 and Sub R-Y/B-Y/Y from I404.
Combines the two sets of signals (Main and Sub).
Converts output signals to 2H (31.75kHz) Y/Pb/Pr unless signals are already 31.75kHz or higher.
YCbCr to YIQ Converter
Consists of QX22-QX27, QX52-QX55
Level/phase shifts color difference signals.
IX02 - YCbCr / YIQ Select IC
Selects either YCbCr or YIQ color difference signals.
YIQ is selected by microprocessor via I004 DAC2 sensing NTSC input on Comp 1 or 2.
Outputs to IX01.
IX01 - Rainforest IC
Receives the three color difference signals from IX02.
Outputs to the three CRT PWBs.
Note: Three Color Difference signals can be:
RGB
R-Y/B-Y/Y
CrCbY
PrPbY
YIQ
YUV
CHROMA ROTATION CIRCUIT EXPLANATION
QUESTION:
What is the function of
QX22, QX23, QX24, QX25, QX26
and
QX27
on the output of the 3D Y/C
Combfilter.
ANSWER:
The RGB Processor
IX01
(TA1298AN) has a function called Skin Tone correction. This circuit is also
named Auto Color or Auto Flesh Tone. The Auto Color function works only with Y/I-Q signals. The
YUV signal out of the Comb filter must be converted to YIQ before entering IX01 (Rainforest IC) in order
to use Auto Color. Y Pr/Pb YUV signals must be converted. IQ signals are made from UV signal by
giving them a 33 degree phase shift.
The Switching IC
IX02
shown on the Chroma After Flex Converter Diagram selects either the NTSC Y/IQ
signal without rotation or the
Y Pr/Pb
with rotation as determined by the control signal
Select 5 (SEL5
).
Select 5 logic: High = Y/IQ (NTSC) and Low = YUV (Y/Pr/Pb).
Not shown is the input pin for
Select 5 (SEL5)
control signal. This control signal is in-put via pin
(5
and
1
2).
