Section VI. EIA TEST THEORY

TM 9-4931-363-14&P

variable resistors R8, R7, and R10 of the test set divider

2-11. General.

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

NOTE

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.

9-1270-212-14&P

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

NOTE

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.

2-18