Amplifier Card A13 Test Theory.

9-4931-363-14&P

return is provided at J9-41. With S9 set to position R2, the

2-18. Amplifier Card A13 Test Theory.

output of AR8 on the A13 card is connected through J9-3,

a. Reference Material. The following reference

through contact 10 and wiper 1 of S4-1, through contacts 2

materials are required to support the amplifier card A13

and 3 of S9, and through contact 2 and wiper 1 of S5-A to

test theory discussion:

the meter and to the channel B input of the oscilloscope

through J11. The oscilloscope channel A input is connected

(1) Amplifier card A13 test table from TM

to J14. The oscilloscope external trigger is connected to

9-1270-212-14&P

J13. With a known input signal amplitude to the A13 card,

amplifier AR8 is adjusted in phase and amplitude until the

signal at J9-3 (oscilloscope channel B) is in phase and equal

(2) Amplifier card A13 foldout schematic diagram

to the input signal, or unity gain.

from TM 9-1270-212-14&P

(5) Refer to step 4 in figure 2-12 and in the A13 test

(3) Amplifier card A13 test functional diagram (fig.

table. Setting S9 to position R3 connects the output of

2-12).

amplifier AR6 on the A13 card through S9-13 and through

contact 10 and wiper 1 of S4-H to the display circuitry

b. Theory Discussion.

described above. In this step, amplifier AR6 is adjusted in

(1) To prepare for the amplifier card A13 test theory

phase and amplitude for unity gain.

discussion, refer to the troubleshooting procedures for

(6) Refer to step 5 in figure 2-12 and in the A13 test

amplifier card A13 in TM 9-1270-212-14&P and mentally

table. Setting S4 to position 8 connects 5 volts ac, out of

perform steps a through e.

phase, through wiper 1 and contact 9 of S4-G, and through

wiper 2 and contact 11 of S7-E to J9-31 and -37 to energize

(2) Refer to step 1 in figure 2-12 and in the A13 test

the circuitry associated with AR1-AR2 and AR3-AR4 on

table. The A13 amplifier card under testis connected to J9

the A13 card. Setting S8 to position 9 applies a ground

on the test set. Setting S3 to position 4 connects 5 volts ac

J9-29 and -35 through contact 10 and wiper 1 of S8-K.

from the voltage divider network R3 and R4 associated

Card operating power is connected as previously discussed.

with T2 through contact 5 and wiper 1 of S3-L, through

With S9 set to position R2, the output of AR4 on the A13

contact 3 and wiper 1 of S4-1, through contacts 2 and 3 of

card is connected through J9-27, through contact 9 and

S9 set to R2, and through S5-A to the meter and A2 card

wiper 1 of S4-I, and through S9 and S5 previously discussed

phase detector circuit for readout. This measurement

to the meter and channel B oscilloscope input. The 9-volt

establishes the exact amplitude of the test set signal which

ac phase reference signal from the wiper of R8 remains

is used as a reference in setting the gain of amplifiers on the

connected through J14 to the channel A oscilloscope input,

A13 card.

Thus, by comparison to the step 4 and 5 reference signal,

this reference will be about 4 volts larger than the channel

(3) Refer to step 2 in figure 2-12 and in the A13 test

B waveform. The A13 test table contains a note advising

table. Setting S3 to position 6 connects the signal at the

the operator of this difference. In this step, output

wiper of R8 in the voltage divider network associated with

amplifier AR4 is adjusted in phase and amplitude for unity

T2 through contact 7 and wiper 1 of S3-L, and through the

connections described above to the meter and phase

gain.

detector circuit for readout. This measurement establishes

(7) Refer to step 6 in figure 2-12 and in the A13 test

the exact amplitude of the test set reference signal used in

table. Setting S9 to position R3 connects the output of

setting the gain of the A13 card amplifiers.

amplifier AR2 on the A13 card through J9-33 and through

(4) Refer to step 3 in figure 2-12 and in the A13 test

contact 9 and wiper 1 of S4-H to the oscilloscope and

meter for readout. In this step, output amplifier AR2 is

table. Setting S7 to position 3 connects the ac output from

adjusted in phase and amplitude for unity gain.

the wiper of R8 through wiper 1 and contact 4 of S7-E to

J9-9 and -23 to energize the circuitry associated with

(8) Refer to step 7 in figure 2-12 and in the A13 test

AR5-AR6 and AR7-AR8 on the A13 card. Refer to the

A13 foldout schematic in TM 9-1270-212-14&P. Setting S8

table. Setting S7 to position 2 connects 9 volts ac, out of

to position 8 applies a ground to J9-11 and -25 through

phase, from the wiper of R8 through wiper 1 and contact 3

of S7-E to J9-37 and -31 to energize the noninverting input

wiper 1 and contact 9 of S8-K. Card +18-volt dc operating

of AR1 and AR3. Wiper 2 and contact 9 of the same switch

power is connected to J9-2 through wiper 1 and contact 10

connect 5 volts ac, out of phase, to J9-35 and -29 to

of S4-J. Card -18-volt dc operating power is connected to

J9-28 through wiper 1 and contact 10 of S4-L. The signal

energize the inverting input of AR1 and AR3. The A13

2-59