MIL-PRF-1/1313G
TABLE I. Testing and inspection - Continued.
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The fixture described in Drawing 284-JAN shall be used to hold the tube in the manner indicated. The tube shall be subjected
to the specified acceleration in the X, Y, and Z axes, with six shocks in each axis. Tubes showing any permanent shorts, or
more than one temporary short during the test, shall be rejected. The applied shock shall be an approximate half-sine wave
motion with duration measured at the zero-axis level.
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This test shall be performed during the initial production and then annually thereafter. Sample shall consist of three tubes with
an acceptance number of zero. In the event of a failure, the test will be made as a part of conformance inspection, part 2,
acceptance level 6.5 of MIL-PRF-1 Table III . The annual sampling plan shall be reinstated after three consecutive samples
have been accepted.
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During the performance of life-test (5), the rf grid driving voltage and the bias voltage shall be monitored and held constant.
The bias voltage shall be adjusted to produce the specified value of Ibo and the rf drive shall be adjusted to produce the
specified anode current of 250 mA dc during an initial adjustment period not to exceed 4 hours. In no case shall the grid be
driven positive with respect to the cathode as indicated by a grid current of 50 µA dc maximum. At the conclusion of the life-
test period, the change (ĆIb) in the anode current from the initial value of 250 mA dc, and the power output (Po), both being
read in the life-test equipment itself, shall be read and the tube shall meet the listed requirements for these parameters. Prior
to the performance of life-test (5), the tube shall have met the requirements of the linear amplifier power output and distortion
test.
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Heater voltage shall be cycled approximately 2.0 minutes "on" and 4.0 minutes "off". No grid-cathode shorts are permitted
during or after life test. For qualification, data on a sample of 10 tubes shall be submitted.
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The tube shall be mounted in an air-system socket (EIMAC SK-710, with SK-606 chimney, or equivalents) arranged so that
the entire airflow passes through the anode cooler, with air flowing in a base-to-anode direction. Air under standard
conditions of temperature and pressure shall be used, or appropriate correction applied. Temperatures shall be measured by
means of thermocouples, located as follows:
Anode core. The thermocouple shall be embedded in the top of the anode core, adjacent to the cooler, by means of drilling a
small hole, shallow enough so that the tube vacuum shall not be lost, placing the welded thermocouple junction therein, and
then peening the edges of the hole so as to hold the thermocouple firmly in place.
Anode seal. The thermocouple shall be attached, by any suitable means, to the base of the anode in the immediate vicinity of
the junction of the screen-grid/anode insulating dielectric material with the anode.
Base seal. The thermocouple shall be attached, by any suitable means, to the screen-grid contact where it joins the insulating
dielectric material.
In all cases, good electrical continuity between the thermocouple and the metal area in close proximity shall be demonstrated
before the cooling test is performed.
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Measurement with General Radio Megohmeter Model 1862C, or equivalent. Unused elements are to be left floating.
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