MIL-PRF-1/1335H
TABLE I. Testing and inspection - Continued.
Inspection
Method
Notes
Conditions
Acceptance
Symbol
Limits
Unit
MIL-STD-1311
Level
12/
Min
Max
Conformance inspection,
part 3 - Continued.
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Group A; stability life-
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1501
Intermittent life
test conditions;
t = 1,000 hours
Intermittent life-test
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end points:
mA
264
222
If
Heater current
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1301
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6,500
Sm
Transconductance (1)
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1306
µmhos
30
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Change in trans-
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1306
ĆSm
%
conductance (1) of
t
individual tubes
20
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Transconductance (2)
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1306
%
ĆSm
Ef
20
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1336
Heater-cathode
Ihk
µA dc
leakage
MegΩ
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50
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1221
Insulation of
R
electrodes
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Shock
1041
11/
Hammer angle = 30°;
Ehk = 50 V dc;
Eb = 150 V dc;
Rk = 82 ohms;
Ec = 0
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Shock-test end points:
mV ac
15
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Ep
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1031
Low-frequency vibration
20
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Ihk
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1336
Heater-cathode
µA dc
leakage
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6,800
Sm
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1306
Transconductance (1)
µmhos
258
222
If
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1301
Heater current
mA
If resistance is used in the cathode or anode circuits, the grid circuit resistance may be as high as (10,000 + 100 Rk + 10 Rl)
1/
ohms, where Rk is the cathode-bias resistance in ohms and the Rl is the ac anode load resistance in ohms.
2/
Operation below the rated maximum temperature is recommended for applications requiring the longest possible tube life.
3/
Prior to this test, tubes shall be preheated a minimum of 5 minutes at the conditions specified below. The 3-minute test is not
permitted. Test within 3 seconds after preheating.
Ef
Ecc
Eb
Rk
Rg
V
V dc
V dc
Ohms
Meg
7.0
0
150
82
0.1
4/
The specified voltages shall be applied between the anode and grid.
5/
Sampling and acceptance criteria shall be as follows: Sample shall consist of 15 tubes with an acceptance number of zero (see
12/).
6/
Tubes shall be tested as specified in MIL-STD-1311 method 2126, except that they shall be first immersed in water at not more
than 5°C for 15 seconds and immediately thereafter subjected to the standard temperature cycle specified in MIL-STD-1311
method 2126. Tubes having high-heater current of 300 mA or more shall be rejected as evidence of air leaks.
4
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