MIL-PRF-1/1254E
TABLE I. Testing and inspection - Continued.
1/ The tube shall be subjected to the number of temperature cycles and temperature limits specified. The tube shall be maintained at
each end-point temperature for sufficient time to reach equilibrium, but not for less than 5 minutes. Changes in temperature from
end point to end point shall be gradual but the cycle shall not exceed 30 minutes. After cycling, the tube shall be allowed to return to
room temperature, held for 24 hours, and then shall be tested for the specified limits of ignitor ignition time and ignitor voltage drop.
2/ The minimum temperature rate of change shall be 2.5°C/minute. The test shall be conducted with aluminum flanges (see figure 2)
securely attached to each end of the tube. The ignitor current shall be monitored during the test and shall remain within the limit
specified.
3/ The air pressure specified shall be applied to the input and output window of the tube for a period of 2 hours, after which the
pressure shall be reduced to atmospheric pressure. The pressure is permitted to decrease by 10 percent of the specified value
during the test interval. After this test, the tube shall pass the ignitor voltage test.
4/ The leakage energy shall be measured for each channel individually.
5/ The leakage energy shall be measured for the receiver arm as shown in test circuit A.
6/ During the life test, each channel shall be terminated with 01037-1N23W E silicon diode mounted in a balanced mixer. The diode
will satisfy DSCC Drawing 01037 of the latest issue. The mixers will be mounted as shown in test circuit B. The local oscillator
input during life shall be terminated with 100-ohm video loads. W hen tubes are being life tested at elevated temperatures, the diode
shall be maintained at 25°C nominal.
At the beginning of the life test, the balanced mixers shall each have a noise figure less than 8.0 dB. The mixer noise figures shall
be remeasured periodically during the course of the test. The interval between measurement shall be not more than 100 hours.
Should diode failure occur, the failed diode shall be replaced and the life test continued. If a diode failure occurs during the last 100
hours of the required life test, the failed diode shall be replaced and the life test continued for a minimum of 100 additional hours.
However, only one diode failure per each balanced mixer shall be allowed during the life test. If a failure of the test equipment (keep-
alive-power supply, etc.) occurs and damages all diodes, the diodes shall be replaced and the life test continued. If the test
equipment failure occurs during the last 100 hours of required life test, the diodes shall be replaced and the life test continued for a
minimum of 100 additional hours. The noise figure of the two balanced mixers must remain within the specified limits throughout the
life test.
7/ All measurements that include short-slot hybrids shall be made with gaskets bolted between input and output flanges of tube and
mating flanges.
8/ The tube shall be vibrated in a plane parallel to the ignitor axis under the conditions specified. Input flange shall be rigidly coupled to
the vibrating table, either coupled directly for horizontally vibrating table, or coupled through an "L" shaped mount for vertically
vibrating table. The tube shall be positioned so that both ignitors are equidistant from the vibrating table surface. The output flange
shall be rigidly connected to a standard 12 ± .500 inch dual length of RG52U bronze waveguide with standard dual flanges at each
end. Vibration frequency shall be adjusted in the range specified until resonance is obtained. Vibration shall continue at the
resonant frequency for the specified time. The ignitor voltage drop shall be monitored during the year.
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