MIL-PRF-1/924H
NOTES:
1.
The maximum voltage appearing between any pair of pins shall be no greater than the peak inverse anode voltage rating.
2.
Input choke filter 5-Henries minimum required for 60 Hz power supply.
3.
Input choke filter 10-Henries minimum required for 60 Hz power supply.
4
The tube shall be operated in a vertical position. If mounted in a horizontal position, pins no. 1 and no. 4 shall be in a
vertical plane.
5.
Satisfactory operation of this tube under conditions falling within area I may be obtained without preheating the filament.
For satisfactory operation under the conditions falling within area II, preheat the filament for 10 seconds before the anode
voltage is applied. (See figure 2.)
6.
Inoperatives shall be defined in accordance with the requirements of method 1201. The product shall be stabilized 100
percent at the following conditions for 6 hours as a full-wave rectifier: Ef = 5.0 V ac; Epp/a= 800 V ac; Zp/a = 100-ohms
maximum; R1 = 2,700; tk = 0; C1 = 4 µF. (Under these conditions Io should equal approximately 300 milliamperes dc).
Inoperative control is a triple sampling plan performed on all tubes in the lot. The procedure is: All tubes shall be
stabilized as explained herein. The lot shall then be tested 100 percent for inoperatives. If the percent inoperative during
and immediately following the stabilization period is not more than the acceptance requirements, the lot shall be subjected
to the remaining tests. Otherwise, the stabilization operation shall be repeated. The acceptance requirements for the
three stabilization operations are 3 percent, 2-1/2 percent, and 2 percent inoperatives, respectively. If the lot does not
meet the acceptance requirements after the third test it shall be scrapped. The 6-hour stabilization period includes the
"off" time accumulated during cycling of approximately 15 minutes "on" and 5 minutes "off." Both filament and anode
voltages shall be applied simultaneously at the end of the "off" period.
7.
Test each unit section separately.
8.
This test to be performed at the conclusion of the holding period.
9.
In a full-wave circuit, adjust Zp/a so that a bogey tube gives an Io equal to 260 mA dc and ib not less than 630 mA per
anode. A bogey tube is defined as a tube with a voltage drop of Etd = 75 V dc at Is = 320 mA dc per anode.
10. This test shall be conducted on the initial lot and thereafter on a lot approximately every 6 months. When one lot has
passed, the 6-month rule shall apply. In the event of lot failure, the lot shall be rejected and the succeeding lots shall be
subjected to this test until a lot passes.
11. Preheat tubes with Ef = 5.0 V for 5 minutes minimum prior to testing for Is at EF = 5.0 V. Preheat tubes with Ef = 4.5 V for
5 minutes minimum prior to testing for Is at Ef = 4.5 V.
12. The plane of the filament shall be parallel to the plane passing through the centerline of pins no. 1 and No. 4 within
± 22-1/2 degrees.
13. Envelope temperature (TE) requirements, when measured in accordance with the temperature by conduction-band
measurement (MIL-STD-1311 method 1226), will be satisfied if a tube having bogey Etd (±10 percent) under normal test
conditions, is determined to operate at or above minimum specified temperature at any position in the life-test rack.
14. Intermittent life test.
(a)
The intermittent life-test sample shall consist of 20 tubes. At the completion of 500 hours (+48,
-24 hours), the first 10 serially marked operative tubes shall continue on for the 1,000-hour life
test. The 1,000-hour life test shall be conducted on a minimum of 1 sample of 10 tubes each
month of production.
(b)
In the event of failure of the first sample on intermittent life test, a completely fresh sample of 40
tubes shall be selected. At the completion of 500 hours (+48 hours, -24 hours), the first 20
serially marked operative tubes shall continue on for the 1,000-hour test.
(c)
Life-test samples shall be selected from a lot at random in such a manner as to be representative
of the lot. If such selection results in a sample containing tubes which are outside the initial limits
of this specification sheet for the relevant life-test end point characteristics, such as tubes shall be
replaced by randomly selected acceptable tubes.
(d)
Serially mark all tubes from the sample.
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