Sharp CV-3709S Serviceanleitung Seite 60

3. Switching of colour difference signal between PAL
system and SECAM system (see Fig. 3)
In the SECAM unit, the signals R-Y and B-Y which have
been subject to the demodulation
pins @ and @ of IC931 to enter the matrix circuit, where
the signal G-Y is produced. Then the SECAM colour
difference signals are supplied to CRT drive circuit.
In the PAL IC (IC801) are also produced
difference signals B-Y, R-Y and G-Y, and the signals B-Y
and R-Y alone are fed to the SECAM
the signal G-Y to enter the SECAM unit, J158 is cut off
to make open the output of pin @ of IC801. J156 and
J157 are also cut off to enable switching
colour difference signals R-Y and B-Y to the CRT drive
circuit. Both signals R-Y and B-Y are sent to pins @ and
@ of IC931, and they are supplied via the system switch
II to the matrix circuit where the signal G-Y is produced
to be fed to the CRT drive
circuit and DC clamp circuit.
The reference voltage available at the brightness circuit
4. Horizontal/vertical blanking
There are produced the horizontal
vertical output pulse in the PAL unit; the former pulse is
resulted from FBT pulse which
the output waveform of 12Vp-p. Both pulses are sup-
plied via the connector JD to the SECAM unit.
In the SECAM unit, the vertical
sed by D935, R977 and C966 to produce a flyback pulse
which is mixed together
pulse to enter pin O of IC931. The mixed pulse is then
separated into the horizontal
that they are independently
tal pulse is also used to drive
IC931.
process are applied to
the colour
unit. Not to allow
of the PAL
circuit via the colour control
pulse
blanking pulse and
has been shaped to have
output pulse is proces-
with the horizontal blanking
pulse and vertical pulse so
used in IC931. The horizon-
the flip-flop circuit
in IC801 is connæted to the G-Y output pin of IC931 via
the connector JB: this connection is enabled by cutting
off J158.
The CRT drive unit has been factory adjusted, and
generally it is not needed to perform
CRT drive mechanism due to quality dispersion Of CRT.
When the SECAM
readjustment is necessary only for the colour difference
output level between
voltage caused
electrical connection
unit. connect the connectors
figure 3 Switching of Colour
SECAM Systems
5. Gate pulse
The gate pulse available
make sampling of ID (Identify) signal in the SECAM unit.
The mixed signal of gate pulse and horizontal blanking
pulse is sent to Zener diode (D932) where the horizontal
blanking pulse is eliminated and the gate pulse alone is
picked up to be supplied
The vertical output
shaped in waveform
to activate the ID gate (Frame ID) operation during the
vertical period.
in
4
readjustment
unit is connected to the TV set,
IC931 and IC801, and for the bias
by R853, R859 and' R865.
between the SECAM unit and PAL
JB and JC between
Difference Signal between
at pin @ of IC801 is used to
to pin @ of IC931.
pulse applied to the SECAM unit is
and then is sent to pin @ of IC931
of
To allow
them.
PAL and