Following is the protect circuit Samsung TV which use IC LA76931 as basic working the protect circuit. This Protect Circuit LA76891 located at pin-30 whichconnected to the collector of transistor Q902.In normal conditions the voltage at the base of Q902 is “low” and the voltage at pin-30 is “high”. For the temporary crippling protect, it can be removed Q902 (or to the emitter-base short).
|SAMSUNG protect circuit with LA76931|
Sampling circuit protect from:
Vertical Protect. Pulses of the vertical-out rectified by diode D355, so that the base voltage is approximately 0.6V Q904 ,and collector voltage is 0v.
X-ray Protect (option). Sampled using a heater voltage of the circuit as shown below. Normal vltage in x-ray path to the base of Q902 is zero.
ABL protect. If there is damage to flyback voltage which can cause a high rise ABL, then protect circuit will actively work.