MIL-PRF-1/1331F
TABLE I. Testing and inspection - Continued.
Inspection
Method
Conditions
Acceptance Symbol
Limits
Unit
MIL-STD-
level
10/
Min
Max
1311
Conformance inspection,
part 3 - Continued
Inch of
1155
No voltages 4/ 9/
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0.60
Coolant pressure drop versus
water
coolant flow (forced air)
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Shock, specified pulse
1042
No voltages;
accel = 15G peak (min);
D = 11 ± 2 ms
half-sine wave 8/
Shock, end points:
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Electrode voltage (grid)
1261
---
Ec1
-32
-46
V dc
Total grid current
1266
---
Ic1
---
-15
µA dc
Sweep-frequency vibration
1031
No voltages; 10 G;
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F = 25 to 2,000 Hz 8/
Vibration end points:
---
1261
Electrode voltage (grid)
---
Ec1
-32
-46
V dc
1266
Total grid current
---
Ic1
---
-15
µA dc
1/
W hen the tube is operated at 100 percent of maximum rated anode dissipation at an incoming air temperature of 25°C maximum, a
minimum airflow of 5.6 cfm at sea level shall pass through the anode cooler. The static pressure drop across the anode cooler at
this flow is approximately 0.26 inch of water. If the socket on Drawing 246-JAN is used, an incoming airflow of 5.6 cfm to the grid
end of the socket is required. At this flow of 5.6 cfm, the static pressure drop directly across the tube and socket is approximately
0.60 inch of water. This pressure drop varies with the amount of escaping air and with the shape and construction of the air
director. The airflow rating applies at bias voltage less than 100 volts and frequencies less than 500 MHz. Air cooling of the tube
shall be increased with increased negative grid bias, increased incoming air temperature, or increased frequency of operation, or a
combination. In all cases of operation, a socket which provides forced-air cooling of the base shall be used and maximum seal and
radiator temperature ratings shall not be exceeded. The airflow shall be applied before or simultaneously with electrode voltages,
and may be removed simultaneously with them.
2/
The filament voltage is 26.5 ± 10 percent but when long life and consistent performance are factors, it is recommended that the
voltage be held at ± 5 percent. Maximum life may be obtained by adjusting the heater voltage in accordance with the application. A
table of heater voltage versus frequency is presented as a guide.
Frequency (MHz)
Ef (Vac)
Up to 300
26.5
301 to 400
25.5
401 to 500
24.3
3/
In all cases of electrical tests involving application of heater voltage, the socket on Drawing 246-JAN shall be used. An incoming
airflow of 6.0 cfm maximum to the grid end of the socket is permitted.
4/
An infinite baffle system as shown on figure 2, or equal, with an airflow of 5.6 cfm at sea level shall be used. The static pressure
drop is measured across the tube and socket.
5/
This test is to be the first test performed at the conclusion of the holding period.
6/
Circuit and cavity shall be in accordance with Drawing 223-JAN.
7/
This test shall be made a minimum of 30 minutes after Ef is turned off. Rated airflow shall be maintained during the 30-minute
interval.
4
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