TM 11-6625-3041-30/T0 33A1-8-908-12
1-23. AC INPUT (A2) FAULT SENSING (CONT)
If the 150V Supply is low or if any of the four dc supplies
Supply
Fault
from the Multi VDC card are low, the input to the Supply
Driver
Fault Driver at Q24 base is high. With its base high, Q24
turns on and lights POWER SUPPLY alarm lamp DS2 on the front
panel of the SG-1139.
Ext Fault
If any of the four logic cards have sensed a fault, the input
to the Ext Fault Sens at U1-11 will be low. Since the negative
Sens
input at U1-10 is high, the output of U1-13 will be low. This
sets the output of the Ext Fault Sens at U8-15 high.
If any of the dc supplies are out of tolerance, the input to
System
the System Fault Driver at U6-9 will be high. If any of the
Fault
Driver
four logic cards have sensed a fault, the input to the System
Fault Driver at U6-8 will be high.
If either input is high the output at U6-10 is low, which sets
the output of U8-12 high and the output of U8-10 low. With
U8-10 low, Q3 turns off and deenergizes K1. This provides
FAULT alarm lamp DS3 on the front panel of the SG-1139 with a
return through K1-B3 and B2 and lights DS3.
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