Buffer Amplifier Test Theory.

TM 9-4931-363-14&P

2-13. Buffer Amplifier Test Theory.

2-14. Sequencer Card A9 Test Theory.

a. Reference Material. The following reference

a. Reference Material. The following reference

materials are required to support the sequencer card A9 test

materials are required to support the buffer amplifier test

theory discussion:

(1) Sequencer

card

test

table

from

table from TM

(1) Buffer amplifier test

9-1270-212-14&P

(2) Sequencer card A9 foldout schematic diagram

(2) Buffer amplifier schematic diagram from TM

from TM 9-1270-212-14&P

9-1270-212-14&P

(3) Sequencer card A9 test functional diagram (fig.

(3) Buffer amplifier module test functional diagram

2-8).

(fig. 2-7).

b. Theory Discussion

b. Theory Discussion.

(1) To prepare for the sequencer card A9 test theory

discussion, refer to the troubleshooting sequencer card A9

(1) To prepare for the buffer amplifier test theory

procedures in TM 9-1270-212-14&P and mentally perform

discussion, refer to the troubleshooting procedures for

steps a through d.

b u f f e r amplifier modules A1 through A8 in TM

9-1270-212-14&P and mentally perform steps a through e.

(2) Refer to step 1 in figure 2-8 and in the A9 test

table. The A9 sequencer card under test is connected to J7

(2) Refer to figure 2-7 and to step 1 in the buffer

on the test set. With S8 set to position 5, 5 volts dc is

amplifier test table. The buffer amplifier module under test

connected from XA12-32 through wiper 1 and contact 6 of

is connected to J10 on the test set. Both channels of the

S8-F to J7-1. The signal return from the card is connected

buffer amplifier are excited through wiper 1 and contact 4

to J7-41. Wiper 1 and contact 6 of S8-B apply a ground to

of S4, banks D through G, and through wiper 1 and contact

J7-24, which inhibits the skip function on the card. J7-11

12 of S3, banks A through D, to the buffer amplifier under

and J7-13 are also grounded through CR16, which enables

test. The outputs from the buffer amplifier under test are

decoder U10 on the card. Setting S5 to position 8 connects

connected through wiper 1 and contact 12 of S3, banks C,

the enable A signal at J7-10 through contact 8 and wiper 2

E, F, H, and I, to the test set resolver. With S9 set to

of S5-B to J12 on the test set front panel. An oscilloscope

position R2, the R2 output of the test resolver is connected

is connected between J12 and J18 as shown in figure 2-8.

through S5-A to the meter and A2 card for readout.

Pressing S11 connects 28 volts dc through wiper 1 and

contact 7 of S4-B, and through wiper 1 and contact 6 of

(3) Refer to figure 2-7 and to step 2 in the buffer

S8-F to energize K8 in the test set. Contacts 2 and 1 of K8

amplifier test table. When S11 is pressed, 28 volts is applied

apply a ground to J7-6 causing the reset signal to go low

through W1 and contact 4 of S4-B to J10-1, energizing K1,

momentarily. Refer to the A9 foldout schematic from TM

K2, and K3 in the buffer amplifier. This connects the

9-1270-212-14&P. The momentary low resets the logic

out-of-phase signals at J10-17 and -22 to the buffer

circuitry on the card, and when the switch is released, the

amplifier. With S9 set to position R2, the R2 output of the

logic circuitry begins a normal count. Since the skip signal

test set resolver is connected to the meter and A2 card for

is low, the count from U10 proceeds in a normal sequence.

readout.

When U10-13 goes low, counter U4 is inhibited by lows at

pins 7 and 10 and the count stops automatically. The two

(4) Refer to figure 2-7 and to step 3 in the buffer

enable-A signals will be displayed on the oscilloscope. S11

amplifier test table. With S9 set to position R3, the R3

can be pressed repeatedly as required to display the pulses.

output of the test set resolver is connected to the meter and

A2 card for readout.

(3) Refer to step 2 in figure 2-8 and in the A9 test

table. With S5 in position 2, the enable-B signals at J7-8 are

(5) Refer to figure 2-7 and to step 4 in the buffer

connected through contact 9 and wiper 2 of S5-B and

amplifier test table. When S11 is pressed and S9 is set to

through J12 to the oscilloscope. The timing sequence of

position R3, the R3 output of the test resolver is connected

step 1 is repeated by momentarily pressing S11 repeatedly,

as required to display the enable-B signals.

to the meter and the A2 card for readout.

2-37