TM 11-6625-486-14&P
amplifier.
An externally generated af signal is
substituted for the signal normally present.
the vtvm ac probe. Turn the vtvm FUNCTION switch to
Ground one side of the AN/URM-127 at a convenient
AC and the RANGE SW to 3V.
point on the frequency meter chassis and connect the
(1) Turn the frequency meter FUNCTION SW
other side to the test point indicated.
to CHK and the RANGE SW to A. With the TUNING
CAUTION
control, turn the frequency meter to the 250-kHz
In this equipment, the transistors can
checkpoint (horizontal arrow pointing to right). Turn the
be damaged by excessive input
CORRECTOR control to the midrange.
signals. Do not apply input signals
greater than the levels specified in
(2) Refer to figure 6-10 and measure the ac
the tests below.
signal on the collector of Q301. The vtvm should
indicate 2.3 volts.
(3) With the vtvm ac probe, measure the ac
PHONES jack.
signal at the collectors of Q401, Q402, and Q403. The
vtvm should indicate ac signals of 1.5 volts on Q401,
OPER and the RANGE SW to any range. Turn the
1.4 volts on Q402, and 1.6 volts on Q403.
AUDIO GAIN control fully clockwise.
c. Adjust the AN/URM-127 for 1,000 hertz and the
Audiofrequency (af) signal substitution procedures help
ATTENUATOR control for an output signal of
to localize troubles to a section or stage in the audio
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