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(2) Left-right Asymmetrical Correction (LIN coil)
In the circuit shown in Fig. 9-9 (a), the deflection coil
current iH does not flow straight as shown by a dotted
line in the Fig. 9-9 (b) if the linearity coil does not
exist, by flows as shown by the solid line because of
effect of the diode for a first scanning (screen left side)
and effect of resistance of the deflection coil for later
half period of scanning (screen right side). That is, the
deflection current becomes a sawtooth current with bad
linearity, resulting in reproducing of asymmetrical pic-
tures at left and right sides of the screen (left side ex-
panded, right side compressed).
When a horizontal linearity coil L
1
with a current char-
acteristic as shown in Fig. 9-9 (c) is used, left side pic-
ture will be compressed and right side picture will be
expanded because the inductance is high at the left side
on the screen and low at the right side. The left-right
asymmetrical correction is carried out in this way, and
pictures with good linearity in total are obtained.
Fig. 9-10
Fig. 9-9 Linearity coil
(a)
(b) Deflection coil current
Deflection coil current
(iH)
0
Characteristic of D
Resistance of L
H
(c) Linearity coil characteristic
Linearity coil characteristic
Inductance
(
µ
H)
(Left) (Right)
(Left) (Right)
Current (A)
TR
D Co
L
H
Deflection
coil
FBT
Vcc
iH
Li
Cs
S-character
capacitor
TR
D Co
L
H
L
I
L
C
Cs
(b) Sawtooth wave current
(a)