Panasonic TH-65PX600U Service Manual page 55

Sound SOS Detect Circuit
SOS N
N SOS
The transistor Q2301 monitors the speaker amplifier IC (IC2302). If the IC or one of
the speakers develops a short circuit, a high is output at pin 46 of the IC causing
Q2301 to go into conduction and output a low to the base of Q2300. As a result,
Q2300 comes on and outputs a high to the DG board.
A short circuit of the 15V line causes the diode D2309 to go into conduction. The
base voltage of Q2300 becomes low and a high is output to the DG board.
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