LED Blinks Four Times (HHS Protection)
Figure 46
This protection circuit is incorporated to ensure viewer safety and to safeguard
against CRT damage and catastrophic failures. The Heater Pulse from pin 2 of
the flyback transformer T551 is used to sample the high voltage level. The p
is rectified, filtered, and applied to a voltage divider network that consists of R
and R522
ulse
521
. The DC sample is applied to a sensing circuit inside IC701 on the D-
his output voltage is input to the DG-Board via pin 5 of the connector
D4/A4, and pin 7 of the connector A31. This causes the MPU to activate
shutdown and turn off the AC Relay RL801.
Board via the resistor R1509. IC701 monitors the DC sample at its pin 3 and
compares it to the reference voltage at pin 2. An undesired voltage increase at
pin 3 causes the circuit's output at pin 1 to go high. D1503 clamps the output of
IC701 to keep excessive voltage from reaching the MPU, IC1002, of the DG-
Board. T
84
Summary of Contents for PT47WXD63 - 47" PROJECTION TV
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