LG MC-83A Manual De Uso página 50

2. Horizontal Deflection
1) Basic Horizontal Scan Theory
i1(t1-t2)
Q402
C410
CT
2) Circuit Descriptions
¤ R403, C404 : Snubber Circuit
To decrease ringing by T401 which effects falling
time of driver Tr (Q401)
¤Ł R402 : Determines the base current of Q402
¤Ø C401 : To protect Q402 and T401 from burning out
If its capacitance goes down, sound noise of H-
Drive trans (T401) is going up, the loss of Q402 is
going up and finally Q402 burns out
¤Œ R401 : To control the base current of Q402
3) The equation of horizontal high voltage
t
s
Vcp = Vcc (1+ )
2 t
r
( t = )
C L
r
T y
t
s
= Vcc (1+ ) = Vcc (1+
2
C L
T y
therefore, C414¡ Ł ¡ High Voltage¡Ø ¡ H-size¡Ł
Generally, the capacitance of C414 is going down as time
passes and high voltage goes high and H-size goes narrow.
is
1 3
Primary winding(
i2
of FBT
i3
H-DY
C411
CS
i4
here, t = t -t
s h r
t
s
)
2 C L
T y
t1
B+(115V)
)
1
- 3
i1
- 20 -
t5
t2 t3 t4 t6
t
t
inducde back EMF
Voltage is damped
through damping
Diode in Q402
i2
i4
i3