Panasonic GP6DU - TH-42 XVS30 3.3 V SOS Detect Circuit (D Board); TH-42 XVS30 5 V SOS Detect Circuit (D Board)

TH-42XVS30 3.3V SOS Detect circuit (D board)
Pin 96 of the Microprocessor IC9300 on the D board monitors the 1.5V1, the
1.5V2, and the 3.3V generated on the D board. It also monitors the P12V
generated on the P board. The 12V from the P board is connected to pin 1 and
pin 2 of connector D25.
If the voltage in any of these lines drops, the SOS circuit is triggered.
Under normal conditions, the voltage drop derived from the voltage divider
circuits at the base of Q9003, Q9004, Q9005, or Q9006 is enough to turn the
transistor on. However, if the voltage drop at the base of any of these transistors
decreases, the transistor is turned off. This allows the 5 volts at their collectors to
forward bias transistor Q9009. This effectively grounds pin 96 of the CPU
(IC9003) on the D board, triggering the shutdown circuit.
Under normal conditions, pin 96 of IC9003 is set to high.
TH-42XVS30 5V SOS Detect Circuit (D board)
Pin 95 of the Microprocessor IC9003 on the D board monitors the P5V from the P
board.
If there is a short or the voltage goes low, the voltage drop derived from the
voltage divider circuit goes low and the SOS circuit is triggered.
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