Panasonic Generation Plasma Display Television Technical Manual page 60

SOS Circuit Overview
Protection circuits are incorporated in the unit to prevent the failure of a single circuit or component
from creating catastrophic damage.
1 Blink SOS: This shutdown operation is usually caused by a lack of communication between the A
and the D boards.
1 Blink SOS: This shutdown operation may be caused by the improper connection of a SS board
connector to the panel.
2 Blinks SOS: Pin 87 of the MPU IC9003 monitors the 15V line. During normal operation, the
transistors Q9053 and Q9054 output a high to pin 87. If the 15V line is missing or shorted, a low is
provided to pin 87. As a result, the unit shuts down and the power LED blinks 2 times.
3 Blinks SOS: IC9807 is a 3.3V regulator located on the D board. Its output is monitored by IC9003.
If the 3.3V is not present at pin 86, the MPU shuts down the unit. The power LED blinks 3 times.
5 Blinks SOS: Pin 85 of the MPU IC9003 monitors the 5V line. During normal operation, the
transistors Q9051 and Q9052 output a high to pin 85. If the 5V line is missing or shorted, a low is
provided to pin 85. As a result, the unit shuts down and the power LED blinks 5 times.
6 Blinks SOS: Pin 90 of the MPU IC9003 monitors the status of the SC board. During normal
operation, the transistor Q6581 and IC6581 output a low to pin 90. If the SC board becomes
defective, a high is provided to pin 90. As a result, the unit shuts down and the power LED blinks 6
times.=
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