Toshiba TW40F80 - Manual (Page 64)

64
3-1. +35V Over Current Protection Circuit
The over current protection circuit cuts off the power supply
relay when it detects abnormal current increased in the +35V
power line due to failure of the vertical deflection circuit.
3-1-1. Theory of Operation
Fig. 8-11 shows the circuit diagram of the over current
protection circuit. When the load current of the +35V line
increases, the voltage across a resistor of T370 will also
increase.
Fig. 8-11
When the voltage increases across R370. and the voltage
developed across R371 becomes higher than the Vbs of
Q370, Q370 turns on and a voltage develops across R374
due to the collector current flowing. When this voltage
increases to a value higher than about 7V, Z801 operates,
thus cutting off the power relay. When the circuit operates, a
power LED provided will turn on and off in red.
R372
R370
R371
C370
Q370
2SA933SQ
D421
UZ22BSD
R373
R374
+35V
C310
D302
C303
R327
FBT
pin 6
C371
D370
UZ11BSB
R375
To pin 14 (GATE)
of Z801