Figure 2-2. Test set self-test functional diagram (sheat 1 of 4)

TM 9-4931-363-14&P

signals to a dc level. The negative dc level at the base of Q1

(2) If an in-phase signal (waveform D) is inserted for

keeps the transistor turned off. The negative dc level is

detection at XA2-41, the signal is connected to the

inverting input of AR1. A low-amplitude signal is amplified

applied to the inverting input at AR3-2. The output signal

at AR3-6 (waveform I) is, effectively, a positive dc level,

2.35 times and the output signal at AR1-6 (waveform E) is

which turns on Q3, applying a ground at XA2-37 to light

limited by 5.1-volt zener diodes CR1 and CR2. Thus, a

PHASE 0 indicator DS20 (fig. 2-2, step 7).

low-amplitude signal will retain its original waveshape,

while a signal exceeding 10.2 volts peak to peak will be

limited at that value. The limited and inverted signal is

applied through 200K resistor R4 to the inverting input at

i. Mentally perform step 8 of table 3-3 and refer to step

AR2-2. The theoretical output at AR2-6 (waveform F) will

8 in figure 2-2. Contact 3 and wiper 1 of S3-L connect 10

be an inverted square wave of the same amplitude as the

volts ac, phase angle 180 degrees, through the route

input. The limited and inverted square wave from AR1-6 is

described above to XA2-41. The out-of-phase signal

also connected through R6 and R7 to the noninverting

(waveform J) is limited and inverted by AR1 and appears as

input at AR2-3. Since the input impedance 100K and the

an in-phase signal at AR1-6 (waveform K). The theoretical

load resistance is 200K, the gain of the noninverting input

output of the signal at AR2-2 (inverting input) is an

out-of-phase square wave (waveform L). The theoretical

is 2. The theoretical output at AR2-6 (waveform G)

output of the signal at AR2-3 (noninverting input) is an

consists of amplified negative-going pulses only, since the

positive-going pulses are grounded by the action of the

in-phase amplified square wave (waveform M). The

composite output of the two signals is a series of positive

chopper. The composite output of the two signals at AR2-6

(waveform H) is a series of negative pulses, the amplitude of

pulses (waveform N) that are, effectively, a dc level. The

positive dc level turns on Q1, applying a ground at XA2-35

which is the difference between the two waveforms. The

faltering of R7, C2, and C3, and of C1 and R5, changes the

to light PHASE 180 indicator DS19 (fig. 2-2, step 8).

Figure 2-2. Test set self-test functional diagram (sheat 1 of 4)

2-5