TM 55-4920-402-13&P
Figure 4-8. Phase - Lock Loop Test Setup
(2) Set FUNCTION switch to A, R.P.M. RANGE
switch to X10, and INTERRUPTER LOGIC switch to
SINGLE.
(3) Connect signal input A of function generator. Trig-
ger oscilloscope from function generator.
(4) Set up function generator for a square wave output
of 600 mV peak-to-peak at 41.7 Hz.
(5) Connect oscilloscope input B to TP4 (Fig. 4-7).
Verify the oscilloscope indication is+ 10 volts, +1.0 vdc with
a negative going pulse coincident with the square wave input
rising edge.
(6) Connect oscilloscope input B to TP5 (Fig. 4-7).
Verify that oscilloscope indication is similar to TP4.
(7) Set INTERRUPTER LOGIC switch to DOUBLE.
Verify that pulses at TP5 disappear. Rest INTERRUPTER
LOGIC switch to SINGLE.
(8) Connect oscilloscope input B to TP6. Verify that
oscilloscope indication is 24 sawtooth ramp signals for each
input square wave and that bottom of ramp is approximately
+ 1.5 volts and peak is approximately +5 volts. The amplitude
of the cycle prior to the positive-going edge of the square
wave should be approximately 75% of the amplitude of the
rest of the cycles.
(9) Connect oscilloscope input B to TP7 (Fig 4-7).
Verify that oscilloscope indication is +8 ± 1 vdc with a 30 mV
peak-to-peak triangle waveshape riding on it. The triangle
wave and the input square wave are phased as follows: nega-
tive ramp of triangle simultaneous with negative half of input
square wave.
(10) Set frequency of function generator to 150 Hz.
Verify that delevel at TP7 changes to +4 ± 1 vdc.
(11) Connect oscilloscope input B of TP8 (Fig. 4-7).
Set frequency of function generator to 16 Hz. Verify that
5-volt square wave at TP8 is in phase with input square wave.
(12) Set frequency of function generator to 166 Hz.
Verify that square wave at TP8 changes to 166 Hz and is in
phase with input square wave in approximately 5 seconds.
(13) Connect oscilloscope input B to TP9 (Fig. 4-7).
(14) Set frequency of function generator to 55.5 Hz.
Verify that wave from at TP9 is a 4-volt square wave at twice
input frequency. Square wave is 0 volts for 3 ms and 4 volts
for 6 ms. This two-to-one ratio exists for all frequencies from
16 to 166 Hz.
f. Counter-Decoder Tests.
(1) Add a second function generator to test setup and
connect to CHANNEL A accelerometer input as shown in
figure 4-9.
(2) Connect oscilloscope input A to function generator
2 and setup function generator 2 for a 55 Hz sine wave output
at minimum output.
(3) Connect oscilloscope input B to function generator
1 and setup function generator 1 for a 55 Hz square wave out-
put.
(4) Set R.P.M. RANGE switch to X10 and R.P.M.
TUNE dial to 330.
(5) Increase output level of function generator 2 until
IPS meter indicates between 0.2 to 0.5 IPS.
(6) Increase frequency of function generator 1 to
slightly above 55 Hz until Phazor lamps step around in a
counterclockwise direction in approximately 1 second with no
skips or pauses.
(7) Change frequency of function generator 1 until
rate of rotation is approximately one lamp per second. Verify
that lamps illuminate approximately one lamp per second.
Verify that lamps illuminate in sequence with no skips or
pauses.
4-10
Change 8
