Panasonic EURO 4 Chassis, Technical Manual

Page: 19 / 163

3DQDVRQLF
19
9.3. East/West Correction
To compensate for the pincushion distortion in
east/west direction in the case of 110
•
sets, the
horizontal deflection current must be increased at
vertical centre in relation to vertical start and vertical
end.
This correction is achieved by the horizontal
deflection current being influenced with a vertical
frequency parabola in the east/west diode modulator
D551, D552.
Output from the VDP IC601 , pin 32 a parabola
waveform of 1v pp occurs which is passed via R847
to buffer transistor Q701 before being input via pin 7
of the East / West IC. IC701 .
Here the parabola waveform is fed to a comparator,
where the parabola waveform is compared with the
horizontal flyback pulse, from the output of the
comparator the E/W drive signal is output via pin 5
and fed to the diode modulator via R702 and the
E/W charging coil L701.
This E/W signal is then superimposed onto the
deflection current with the aid of
the diode
modulator, thus performing E/W correction.