MIL-PRF-1/1640E
TABLE I. Testing and inspection - Continued.
1/ This specification sheet uses accept on zero defect sampling in accordance with MIL-PRF-1, table III.
2/ Prior to the application of high voltage, the cathode shall be heated to the required initial operating temperature.
This shall be done by applying 13.75 volts ± 5 percent for 150 seconds maximum. Upon the application of anode
voltage, the heater voltage shall be reduced according to the following schedule:
Ef(V) ±5 percent
Du
Ib (mA dc)
Standby
----
----
13.75
Operate
0.001
27.5
0
For Pi equal to or greater than 450 watts, Ef = 0
For Pi less than 450 watts, Ef = 13.75 (1 - Pi) ± 10 percent
(450)
3/ The characteristics of the applied pulse shall be those which result in proper starting and oscillation. The rate of
rise of the voltage pulse, the percentage of pulse voltage ripple, and the rate of pulse voltage fall are among the
more important considerations. (See method 4304.)
4/ The rate of rise of voltage (rrv) shall be measured in accordance with method 4304, except that the steepest
tangent to the leading edge of the voltage pulse shall be measured above the 70 percent amplitude point.
5/ In handling and mounting the magnetron, care shall be exercised to prevent demagnetization. (See figure 1.)
6/ This test shall be performed during the initial production and once each succeeding 12-calendar months in which
there is production. Six (6) samples shall be used, with an acceptance on zero failures. In the event of failure,
the test will be made as a part of conformance inspection, part 2, with an acceptance on zero failures. The
regular "12-calendar month" sampling plan shall be reinstated after three consecutive samples have been
accepted.
7/ With a total airflow of approximately 40 cfm at approximately 760 mmHg, divided equally and directed through
the cooling fins toward the body of the tube from two .750 inch (19.05 mm) ducts placed .500 inch to .750 inch
(12.7 mm to 19.05 mm) from the cooling fins, the rise above ambient temperature specified herein shall not be
exceeded.
8/ The frequency shall be the frequency of minimum power output between F1 and F3.
9/ The tube under test (TUT) shall be mounted in a resonance free jig and vibrated with sinusoidal excitation in
each of three mutually perpendicular axes through the following amplitudes for both resonance and cycling tests:
50 to 500 Hz at 5G.
Cycling test: The frequency shall increase from 50 to 500 Hz with approximately logarithmic progression, and
shall require approximately 10 minutes to traverse the range. Frequency shall then decrease from 500 to 50 Hz
in the same manner. This constitutes one cycle. The TUT shall be vibrated for three such cycles in each of the
three axes.
Resonant test: Mechanical resonant frequencies of the magnetron shall be determined during the cycling test.
The TUT shall then be vibrated at the indicated resonant conditions for a period of 30 minutes. If more than one
resonant frequency is encountered, the test period may be accomplished at the most severe resonance, or the
period may be divided among the resonant frequencies, whichever is most likely to produce failure.
10/ The TUT shall be mounted in a resonance free jig and vibrated with sinusoidal excitation in each of three
mutually perpendicular axes through the following amplitudes:
15 to 30 Hz at 0.1 - inch angular displacement
30 to 500 Hz at 2G
The frequency shall increase from 15 to 500 Hz then decrease to 15 Hz with approximately logarithmic
progression, and shall require approximately 15 minutes to traverse the range. Inter-pulse frequency stability
and rf stability shall not exceed the limits specified herein.
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