Panasonic PT-53TWD63, Technical Manual

Page: 90 / 99

Spot Killer
Heater
20V
220V
Figure 48
The spot killer circuit is used to eliminate the bright spot that remains on the CRT
after a tele
line and the r
RT socket integrate to turn on
transistor
C301 to charg
en the unit is turned
off, the 20 Vo g its
collector to go shunt the
20 volts source to ground. This effectively provides a path for the discharge of
vision receiver is turned off. During the operation of the unit, the 20V
ectified AC voltage of pin G1 of the C
Q303. When this transistor is on, Q301 turns off allowing the capacitor
e to the full potential of the 220Vdc source. Wh
lts line goes away and the transistor Q303 turns off causin
high. This high causes transistor Q301 to turn on and
2
capacitor C301 and the grid voltage (G1) of the CRT socket.
86