Panasonic EURO 4 Chassis Technical Manual page 153

3DQDVRQLF
Chapter 4
6.3. AN5422K (IC3901)
The horizontal and vertical pulses as mentioned
earlier are fed to IC3901 pins 13 and 15. Here a
vertical and a horizontal drive pulse are produced and
output via pins 3 and 21.
The horizontal pulse input via pin 13 is fed via a noise
cancellation circuit and sync. separator stage whose
reference is set via pin 11 by R3987/R3983 and
C3939. The horizontal sync. pulse is then output via
pin 10 and input via pin 9 of IC3901 to the AFC stage.
At the AFC stage the horizontal sync. pulse is
compared with the horizontal flyback pulse input via
pin 8. Here the phase is set by adjusting R3938.
The horizontal pulse is then output via pin 7 and input
via pin 6 to the horizontal oscillator stage (the
adjustment for which can be set by R3922) before
being fed via the horizontal driver stage and output via
pin 3.
After the horizontal drive signal is output from pin 3 at
approximately 2.2Vpp the signal is fed via the
complementary Darlington pair connected transistors
Q3902, Q3904. The signal is then fed via the FET
transistor Q3905 to T3901 pin 1 at approximately
250Vpp.
The vertical pulse which is input via pin 15 is fed via
the vertical trigger stage before being passed onto the
following vertical oscillator. The vertical oscillator is
set via pin 16, while the timing of the oscillator is set
via pin 18. From the oscillator stage the vertical pulse
is fed to the vertical drive stage, the amplitude of the
vertical pulse being set by R3927 / R3918 connected
to pin 19.
The vertical pulse is then output via pin 21
synchronised by the vertical flyback pulse input via pin
22. This vertical signal is then fed to the base Q3903.
Transistor Q3903 is then used to generate a parabola
signal of approximately 5Vpp. This parabola
waveform is then fed to the cascade connected
transistors Q3907, Q3906. Here the signal is
amplified to approximately 250Vpp before being fed
to pin 4 of transformer T3901.
The D.A.F. transformer T3901 then combines both
the horizontal sync pulse mentioned earlier with the
vertical parabola waveform. This combined signal is
then output via the HV terminal to the D.A.F. input
terminal of the FBT T551 located on the E-Board.
Here the signal is added to the focus voltage of T551,
the focus voltage VF2 with the D.A.F. waveform signal
which is then supplied to the focus terminal on the
CRT.
By this method the focus voltage for the central and
outer edges of the scan undergo alteration. This
results in the focus voltage for the outer edges being
reduced compared with that of the central area of the
screen, thus increasing the focusing distance of the
beam and enhancing focus at the outer edges.
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EURO 4D Supplement