TM 11-6625-3041-30/TO 33A1-8-908-12
1-23. AC INPUT (A2) FAULT SENSING
+12V Ref
When the +12V Crowbar Q1 turns on, the +12V(J)A Supply drops
Crowbar
to OV which sets the negative input of the +12V Ref Crowbar
Sens
Sens at U1-8 low. This sets the output of U1-14 high, which
turns on the AC Input Fault Driver and lights the FAULT lamp
DS1 on the AC Input card.
150V Low
If the +150V Supply goes low, the U3 transistor turns off, which
Sens
turns on Q5 in the 150V Low Sens. With Q5 collector low, the
output of U2-15 is high, which turns on the AC Input Fault
Driver and lights FAULT lamp DS1 on the AC Input card.
The low level at Q5 collector is also applied to U2-9 and
11 whose output at U2-10 and 12 turns on Q24 in the Supply
Fault Driver and lights the POWER SUPPLY alarm lamp DS2 on
the front panel of the SG-1139.
Board
If either the +12V Crowbar Q1 turns on due to nuclear radia-
Fault
tion or the 150V Supply goes low, the Board Fault Driver Q4
Driver
turns on FAULT lamp DS1 on the AC Input card.
DC Supply
If any of the four dc supplies from the Multi VDC cards are
Fault Sens
out of tolerance, the input to the DC Supply Fault Sens at
U6-1 and 2 is low. With the input low, the output at U6-3
is high and at U6-4 is low. With U6-4 low, the output of
U8-2 and 4 is high, which turns on Q24 in the Supply Fault
Driver. With Q24 on, POWER SUPPLY alarm lamp DS2 lights on
the front panel of the SG-1139.
The output of U8-2 and 4 is also applied to the input of the
System Fault Driver and lights FAULT alarm lamp DS3 on the
front panel of the SG-1139.