Panasonic TH42PX20U - 42" HDTV PLASMA DISPLAY, Информация об обновлении сервиса, Страница: 37 / 70

Protection Circuits
Figure 21
Protection circuits are incorporated in the unit to prevent the failure of a single
circuit or component from creating catastrophic damage.
Transistor Q7541 monitors the UNR21V, UNR14V, +9(S)V, and +5(S)V line. If
any of these supply lines develop a short circuit, transistor Q7541 goes into
conduction and applies a high to pin 69 of the MPU, IC001, triggering an SOS
condition.
Transistor Q7544 monitors the +3.3V, and +2.5V line. If any of these supply lines
increase in voltage transistor Q7544 goes into conduction causing its collector to
go low. As a result, Q7541 conducts and applies a high to pin 69 of the MPU,
IC001, triggering an SOS condition.
The +9(M)V, and +2.5(M)V are also monitored for a drop in voltage. A decrease
in any of these two supply lines forces the respective diode to conduct and
trigger Q7542. A high is applied to pin 69 of the MPU, IC001, triggering an SOS
condition.
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