Blink Sos Circuit - Panasonic TC-L42D2 Technical Manual

When the power button is pushed , IC8001 outputs the TVSUB ON command to turn on the
main power supply and output the power_on voltages. Upon confirmation of the output
voltages of the power supply, IC8001 sends the Inverter_ON command to P board.
On the power supply board, the Inverter_On command enters IC7800, the inverter control IC.
IC7800 then outputs the trigger that turns on the oscillator IC7801. The sine wave output of the
oscillator is provided to the switching transistors connected to T7801 to generate a magnetic
field. The AC output at the secondary of T7801 is provided to the LCD panel via the connectors
P5, P6, P7 and P8 to power the backlights.
When the inverter is operating properly, the inverter SOS input of the micro is pulled low.
If a malfunction occurs, a detection circuit located within IC7800 sends out a SOS command to
alert the inverter control IC, IC7800. IC7800 conveys the SOS message to the main micro
IC8001 by keeping the inverter SOS input high. The TV shuts down and the power LED blinks
1 time.

1 Blink SOS Circuit

Slide # 51