TM 11-6625-847-45
potentiometer A2R5 for an indication of + 1.5 volts.
1-13.
Troubleshooting Common Module ray A1A2 If.
Leave the AN/GRM-50 connected between terminals E2
Amplifier Module A1
and E3 throughout test. Disconnect the ME-26(*)/U from
terminal E5, and connect Voltmeter, Electronic AN/URM-
When troubleshooting amplifier module A1, perform the
145 as directed in the stage gain chart (b below).Compare
general support tests in paragraph 4-10. Refer to figure
the indications on the AN/URM-145 with those listed in the
69 and the troubleshooting chart in paragraph 2-22 for
Output of stage column. Agreement within 10 percent
localizing and isolating malfunctions. When the output of
indicates normal operation. Stage gain is computed by
the if. amplifier module is abnormally low or distorted,
dividing the output voltage of the transistor stage under
make the stage gain measurement as indicated in
test by the input voltage to the transistor stage. The
cumulative gain in decibels of the if.
amplifier is
computed by applying the following formula:
2-14.
Stage Gain Measurements (IF Amplifier
Module A1)
Gain in db = 20 Log E1/E2
Connect test equipment to IF amplifier module as shown
E1 is the output voltage, and E2 is the input voltage to the
in figure 6-20. If a 20-volt dc power supply is not
if. amplifier module. Since the output voltage is 9.6 mv
available, use the +20 volt dc output of the test set as
for an input of 1 mv, the cumulative gain in db is 20 Log
described in paragraph 2-5.
9.6 mv (20 x .9823) which equals 19.65. This result is
within the design specifications of the if. amplifier module
a. Gain Measurements.
Adjust the output of
(gain of 20 0.5 db).
Generator, Signal AN/GRM-50 to 1 0.2 millivolts (mv) at
1.75 megacycles. Connect a Multimeter ME-26(*)/U
between terminal E5 and ground, and adjust 10-kilohm
b. Stage Gain Chart.
Test connections
Voltage (mv)
Stage gain
AN/GRM-50
AN/U RM-145
Input to
Output
stage
of stage
Between E2 and E3 (ground) - Collector of Q3
1
3.2
3.2
Same as above
Collector J3 (Q6)
3.2
9.6
8
Connect the test equipment to the amplifier module under
2-15. Troubleshooting Synthesizer Test Tray A1A3
test as shown in figure 6-21. If a 20-volt dc power supply
(Amplifier Modules AR1 through AR5)
Is not available, use the 20-volt dc output of the test set
as described in paragraph 2-5.
When troubleshooting amplifier modules AR1 through
AR5, perform the general support tests in paragraphs 4-
11 and 4-12. Refer to figure 6-11 and 6-12 and the
a. Gain Measurement. Adjust the output of the
shooting chart in paragraph 2-28 for localizing and
AN/GRM-50 to 50 mv at 1 megacycle and rotate
isolating malfunctions. If any of the outputs f amplifier
potentiometer R1 fully connected the AN/URM-145 ea
modules AR1 through AR5 is abnormally low or distorted
directed in the stage gain chart (b below). Compare the
make the stage gain measurements in paragraph 2-16 to
indication
help localize the fault.
2-16. Stage Gain Measurements, Tray A1A3 (Amplifier
Modules All Through AR5)
2-5
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