Section VI. EIA TEST THEORY
variable resistors R8, R7, and R10 of the test set divider
network through wipers 1 and 2 and contacts 3 and 9 of
S2-B and through wipers 1 and 2 and contacts 3 and 9 of
S2-C, through J2 as six separate signals, and through
The information in this section applies equally
branched test cable W2 by way of connectors P5 and P6 to
to both EIAs (from HSS XM128 and from HSS
connectors J3 and J4 of the EIA. The voltages are
XM136) unless otherwise indicated. See TM
substitution signals for the linkages normally connected to
9-1270-212-14&P for correlation of the EIA
J3 and J4. CR4 also applies 28 volts through wiper 1 and
part numbers with the HSS model numbers.
contact 3 of S2-A to contact 4 of K3. The output of S11 is
connected through wiper 1 and contact 3 of S4-B, through
The following reference materials are required to
wiper 2 and contact 9 of S2-A, and through CR3 to K3.
support the EIA test theory discussions:
When S11 is pressed, the momentary 28-volt signal becomes
a BIT initiate for the EIA and K3 latches. Latched K3
a. EIA test table from TM 9-1270-212-14&P
applies returns for the four indicators that indicate the
status of the EIA.
b. EIA foldout schematic diagrams from TM
d. Refer to step 3 in figure 2-6 and in the EIA test table.
Setting S2 to position 3 breaks the connection to J2-HH to
test the gunner linkage fail logic in the EIA.
c. EIA test functional diagram (fig. 2-6).
e. Refer to step 4 in figure 2-6 and in the EIA test table.
2-12. EIA Test Theory.
Setting S2 to position 4 breaks the connection to J2-Z to
test the pilot linkage fail logic in the EIA.
a. To prepare for the EIA test theory discussion, refer
to the EIA checkout procedures in TM 9-1270-212-14&P
f. Refer to step 5 in figure 2-6 and in the EIA test table.
and mentally perform steps a through f.
Setting S2 to position 2 breaks the connection to J2-HH.
Wiper 1 and contact 6 of S2-D apply a ground through R16
to J1-t, to J2-H, and to XA11, pin 4, in the EIA to force a
simulated buffer amplifier failure.
Where signal nomenclature differs between the
two EIAs, the nomenclature applicable to the
g. Refer to step 6 in figure 2-6 and in the EIA test table.
EIA from HSS XM128 is used as basic signal
With S5 set to position 5 and S8 set to position 4, 14 volts
nomenclature and that for the EIA from HSS
XM136 follows in parentheses.
dc is connected through J1-HH of the EIA, through the test
cable to J1-FF, and through the switches and TB1-3 to the
b. Refer to step 1 in figure 2-6 and in the EIA test table.
meter input. R24 simulates the series dc load of a typical
Wiper 1 and contact 3 of S4-A connect 28 volts dc through
pilot reticle lamp.
CR5 to energize K1 and through CR4 and through wiper 1
h. Refer to step 7 in figure 2-6 and in the EIA test table.
and contact 2 of S2-A to XA2-33 of card A2. If the power
fail signal from the EIA under test through J2-K and J1-q
Setting S8 to position 5 connects 14 volts dc from J2-GG
to XA2-31 is a 5-volt high, the power fail logic circuitry on
of the EIA through J1-GG to the meter. R23 simulates the
the A2 card will provide a ground for DS7 through XA2-27
series dc load of a typical gunner reticle lamp.
and light the indicator. The 115-volt internal power to the
i. Refer to step 8 in figure 2-6 and in the EIA test table.
test set is connected through wiper 1 and contact 3 of S4-C
With S8 set to position 6, the output of the 28-volt
to T1-1 , T2-5, and T3-5.
regulated power supply in the EIA is connected through
J2-W to the meter in the test set.
c. Refer to step in figure 2-6 and in the EIA test table.
With S4 in position 2, power is connected to the EIA as
described in step b. The 28-volt power is also connected
j. Refer to step 9 in figure 2-6 and in the EIA test table.
from S4-A, contact 2, through CR4 to energize K4. When
Setting S8 to position 7 connects -18 volts from the EIA
K4 energizes, it connects three reference voltages from
through J2-b to the meter in the test set.