MIL-PRF-1/1385K
TABLE I. Testing and inspection - Continued.
Inspection
Method
Type
Conditions
Symbol
Limits
Unit
MIL-STD-1311
Min
Max
Conformance inspection,
part 3 - Continued
Shock, specified pulse
---
end points:
µA dc
Total grid current
1266
Ic1
---
-20
1261
Ec1
-70
-100
Electrode voltage (grid)
V dc
2204
7580W Eb = 2,000 V dc;
Po
250
---
W
Linear amplifier power
(useful)
output and distortion
Ec2 = 400 V dc;
Ec1/Ibo = 75 mA dc;
dB
3rd IM
-22
---
Eg1/Ib = 250 mA dc 1-tone; 5th IM
dB
-27
---
RL = 4,000 ± 100 ohms;
Rg = 1,000 ohms (max);
F = 2 MHz (min),
10 Mhz (max); anode
tank Q = 10 to 15;
t = 180 (min) 4/
1/
To obtain maximum life, it is necessary to adjust heater voltage to values indicated below at the indicated frequencies of
operation. These figures are for straight-through amplifier operation. In no case shall the heater be operated at less than 5.4
volts.
Frequency (MHz)
Ef (V ac)
300 or lower
6.00
301 to 400
5.75
401 to 500
5.50
It is recommended that the heater voltage be maintained within ± 5 percent when consistent operation and extended tube life
are factors. This applies to both nominal and derated voltages.
At the specified anode dissipation and an incoming air temperature of 25°C maximum, a minimum airflow, as specified, shall
2/
pass through the anode cooler. At this flow-rate, the static pressure drop across the tube and socket, with an appropriate
chimney (air director) around the anode cooler, is approximately as specified below. The pressure drop varies with the
amount of escaping air and with the shape and construction of the air director. This rating applies at bias voltages less than
100 volts and frequencies less than 500 MHz. Air cooling on the tube base shall be increased with increasing negative grid
bias or with increasing frequency, or a combination of both. In all cases of operation, a socket which provides forced-air
cooling shall be used and maximum seal and anode core temperature ratings shall not be exceeded. The airflow shall be
applied before or simultaneously with electrode voltages, and may be removed simultaneously with them. Where emphasis is
placed on long and reliable life, cooling in excess of minimum requirements shall be used.
Anode dissipation
Airflow
Static pressure
Type
(watts)
(cfm)
drop (inch of water
Socket
at sea level)
7580W
250
3.8
0.30
246-JAN
8930
350
6.0
0.60
246-JAN
3/
In all electrical tests involving application of heater voltage, the use of an air-system socket and forced-air cooling is
permissible.
4/
This test shall be performed yearly. An accept on zero defect sampling plan shall be used, with sample of three tubes with an
acceptance number of zero. In the event of 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 yearly sampling plan may be reinstated after three consecutive samples
have been accepted.
5
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