Toshiba CN27E90 Technical Training Manual page 78

(2) Left-right Asymmetrical Correction (LIN coil)
In the circuit shown in Fig. 11-11 a, the deflection coil
current iH does not flow straight as shown by a dotted line in
the figure 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 pictures at left and right sides of the screen (left
side expanded, right side compressed).
When a horizontal linearity oil L1 with a current characteristic
as shown in figure c is used, left side picture 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
(a)
TR
D
(b) Deflection coil current
Deflection coil current
(iH)
0
(Left)
(c) Linearity coil characteristic
Linearity coil characteristic
Inductance
(mH)
(Left)
Fig. 11-11 Linearity coil
L
H
Co
Deflection
coil
iH Li
Vcc
Cs
S-character
capacitor
Resistance of L
Characteristic of D
(Right)
(Right)
Current (A)
total are obtained.
4-1-3. Horizontal Linearity, M-character Correction
Circuit
Since deflection angle increases with size of picture tube
increases, a M character trend which compresses a picture
image at beginning and end of the scanning will occur. A M
character linearity correction circuit is provided in the N5SS
as shown in Fig. 11-12. The M character linearity correction
is carried out by connecting a series resonant circuit in
parallel with the S capacitor and flowing a resonant current
FBT
H
78
L
H
TR
D Co
L
I
Cs
(b) Sawtooth wave current
Fast Slow Fast Slow Fast
(c) Synthesized current
Fig. 11-12
L
C