MIL-PRF-1/1239F
TABLE I. Testing and inspection - Continued.
1/ Because the cathode is subjected to considerable back bombardment as the frequency is increased, with resultant increase in
temperature, the heater voltage shall be decreased depending on operating conditions and frequency to prevent overheating
the cathode and resultant short life.
2/ Unless otherwise specified, sufficient cooling shall be supplied to maintain anode core and seal temperatures below the
maximum rating.
3/ The maximum dc anode current at the peak of the current curve is 250 mA dc for a signal having a minimum peak-to-average
power ratio of 2.0. The maximum rating for a signal having a minimum peak-to-average power ratio of less than 2.0, such as is
obtained in single-tone operation, is 180 mA dc. During short periods of circuit adjustment under single-tone conditions, the
average anode current may also reach the level of 250 mA dc.
4/ Tube shall be tested in a grid-driven amplifier circuit. Adjust Ec1 bias supply and tune circuit for maximum useful power output.
The specified driver power (Pd) output shall be measured with a Bird Thru-line Wattmeter, or equivalent. Driving power output
equals forward power minus reflected power. Grid voltage supply shall have an effective impedance of 500 ohms maximum.
5/ Before subjection to this test, the tube shall be cooled (room ambient temperature) for 30 minutes. Using the test circuit shown
on the figure of method 1366, measure the resistance, in both directions, between any two adjacent electrodes (except across
the heater terminals). If the resistance value is below that required, repeat this test after a 10-minute interval. If the tube fails
again, the tube shall be rejected.
6/ Cooling shall be set up to maintain the tube temperature at the hottest point on the tube envelope at 225°C ±25°C. (This setup
should be permanent and needs to be verified only as often as required to maintain equipment accuracy.)
7/ With anode, grid 1, and grid 2 tied together, apply a pulse voltage source between anode and cathode. Adjust the pulse
amplitude until the specified peak cathode current is obtained. Test shall be made at the end of 1 minute or when stability is
reached, whichever occurs first. The pulse voltage shall meet the following requirements:
2 µs.
a. Pulse duration:
b. Pulse repetition rate: 60 Hz.
c. Duty factor:
0.00012.
8/ This test shall be performed during the initial production and once each succeeding 12-calendar months in which there is
production. A regular double sampling plan shall be used, with the first sample of three tubes with an acceptance number of
zero, and a second sample of three tubes with a combined acceptance number of one. In the event of failure, the test will be
made as a part of conformance inspection, part 2, code level D, with an acceptance level of 6.5. The regular "12-calendar
month" double sampling plan shall be reinstated after three consecutive samples have been accepted.
4
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business