MIL-PRF-1/1738D
TABLE I. Testing and inspection - Continued.
1/
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 minimum. Upon the application of anode voltage, the heater voltage shall be
reduced to the following schedule:
Du
Ib (mA dc)
Ef (V) ±5 percent
Standby:
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13.75
Test condition 1:
0.0004
11.0
9.0
Test condition 2:
0.0006
16.5
6.0
(1) For Pi between 0 and 375 W , Ef = 13.75 (1-Pi/800) ± 5 percent.
(2) For Pi between 375 W and 600 W , Ef = 19 (1-Pi/600) ± 5 percent.
2/
The characteristics of the applied pulse shall be those which result in proper starting and oscillation. The rate of rise of voltage
(rrv) shall be measured in accordance with MIL-STD-1311 method 4304, except that the steepest tangent to the leading edge of
the voltage pulse shall be measured above the 70 percent amplitude point.
3/
The temperature is to be measured at the point indicated on figure 1 (see notes 5 and 6 of figure 1).
4/
The tuning mechanism shall be capable of withstanding a static torque of 48 inch-ounces at the end of its travel.
5/
The tube under test (TUT) shall be capable of normal operation without electrical breakdown with the input bushing in air at normal
atmospheric conditions.
6/
The minimum air pressure to assure prevention of electrical breakdown in the output coupling shall be 15 psig for voltage standing
wave ratios up to 1.5:1 with phase shift variable over 360 electrical degrees. The tube shall be coupled directly to a UG-52/U
choke flange modified so that mounting holes provide clearance for No. 8 bolts.
7/
The modulator shall be such that energy per pulse delivered to the tube, if arcing occurs, shall not greatly exceed the normal
energy per pulse. The tube heater shall be protected against arcing by use of a connector that places a minimum of 4,000 pF
across the heater directly at the input terminals.
8/
In addition to regular markings, the tuner dial settings for the following frequencies shall be marked on the tube during final testing
by the manufacturer. The accuracy of these settings shall be -10 MHz at the start of life under conditions of test condition 2 with
the body temperature approximately 80°C measured at the point specified on figure 1 when tuning is performed in the order of
decreasing the frequency.
Frequency (MHz)
Dial setting
Frequency (MHz)
Dial setting
8,500
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9,150
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8,650
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9,300
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8,800
---
9,450
---
9,000
---
9,600
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9/
W ith 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 (12.7 mm) to .750 inch (19.05 mm) from the
cooling fins, the rise above ambient temperature specified herein shall not be exceeded.
10/
In handling and mounting the tube, care shall be exercised to prevent demagnetization. Ferromagnetic materials or energized
magnets shall not be brought within 4 inches (101.6 mm) of the tube.
11/
This test shall be performed on four tubes per month when tube is in continuous production, but shipments of the month's
production shall not be held pending completion of the test. So long as three of the four tubes for each of the first three months of
a production run pass the test, and 75 percent of the cumulative quantity of tubes tested pass the test, tubes shall be considered to
conform to this specification. If either of the conditions are not met, shipments shall be halted until three of four tubes of current
production conform to test.
12/
The tuning shaft shall be continuously driven at a speed of 1,400 ± 50 rpm. At the completion of the test, the backlash shall not
exceed 5 MHz. During the test, the tuning shaft may not be lubricated. A cycle consists of two complete excursions each in
opposite directions through the tuning range of the tube.
4
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