MIL-PRF-1/889J
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The socket shown on Drawing 246-JAN 13/ shall be used in all electrical tests involving heater voltage. Forced-air cooling is
permitted at the rate of 4.0 cfm maximum for the base and anode, unless otherwise specified in the specific test conditions. A
separate source may be used for the base and anode, but neither shall exceed 4.0 cfm.
The forced cooling test shall be made as follows: At an ambient temperature of 25°C, both base and anode shall be cooled by
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an airflow of 3.8 cfm maximum at sea level from a single source using the infinite baffle system shown on figure 2, or
equivalent. At the specified test conditions, the anode core temperature shall not exceed the specified limits. Temperature
shall be measured by means of a thermocouple embedded in the top of the core, adjacent to the cooler. This shall be done by
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 to hold the thermocouple firmly in place. In all cases, good electrical continuity
between the thermocouple and the metal area in close proximity shall be demonstrated before the cooling test can be
performed.
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An infinite baffle system (figure 2, or equivalent) with an airflow of 3.8 cfm at sea level shall be used. The static pressure drop
is measured across the TUT and socket.
The input wave shape shall have a tr and tf of 25 μs maximum each, and the slope of the top of the pulse shall not be greater
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than 0.5 percent with a ripple not greater than 0.1 percent.
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This test shall be the first test performed at the conclusion of the holding period.
8/
The circuit and cavity shall be in accordance with Drawing 223-JAN 13/.
9/
This test shall be made 30 minutes after Ef is turned off. Rated airflow shall be maintained during this 30 minute interval.
Measurement with General Radio Megometer Model No. 1862C, or equivalent. Unused elements are to be left floating.
10/ At the conclusion of this test, the TUT shall satisfy the requirements of the total grid current test (method 1266) specified herein
under conformance inspection, part 1.
11/ Revision letters are not used in this revision to identify changes with respect to the previous issue, due to the extensiveness of
the changes.
12/ This specification sheet utilizes an accept on zero defect sampling plan in accordance with MIL-PRF-1, table III.
13/ Contact preparing activity with questions on availability of "JAN" drawings: DSCC-VAT, Defense Supply Center Columbus,
P.O. Box 3990 Columbus, OH 43218-3990.
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