Service manual

The Linearity Correction
A constant voltage across the horizontal deflection coil should result in a linear
increasing saw-tooth current. This however is not the case as the resistance of the coil
is not negligible. In order to compensate for this, a pre-magnetized coil L5421 in series
with the deflection coil is used. This coil ensures that during time interval t1 - t3 the
circuit-resistance will be higher than during t4 - t5. L5421 is called the linearity coil.
To avoid self-oscillation, R3431 and C2431 are placed parallel to L5421.
The S-Correction
Since the sides of the picture are further away from the point of deflection than the
center, a linear saw-tooth current would result in a non-linear image (the center would
be scanned slower than the sides).
To solve this, the deflection current for the right- and left side will be reduced.
C2433 is charged quadratic during time interval t1 - t2. On the left and right sides of the
screen the voltage across the deflection coil decreases, causing the deflection to slow
down. In the center of the screen, the voltage increases and the deflection will increase
in speed.
An S-shaped current will have to be superimposed onto the saw-tooth current. This
correction is called finger-length correction or S-correction. C2433 is relatively small, as
a result of which the saw-tooth current will generate a parabolic voltage with negative
voltage peaks. The current also results in a parabolic voltage across C2421, resulting in
the finger-length correction, proportionally increasing with the picture width. The EW-
DRIVE signal will ensure the largest picture width in the center of the frame. Here the
largest correction is applied. The larger the picture width, the higher the deflection
current through C2433.