MIL-PRF-1/1120G
TABLE I. Testing and inspection - Continued.
1/
For grid-pulse operation, the maximum CW ratings shall apply.
2/
The transit-time heating effect of the cathode shall be compensated for by a reduction in heater voltage after dynamic operation of
the tube has started. The back heating is a function of frequency, grid current, grid bias, anode current, duty cycle, and circuit
design and adjustment. There is an optimum heater voltage which will maintain the cathode at the correct operating temperature
for a particular set of operating conditions. A maximum variation of ± 5 percent from optimum is permitted. No reduction in heater
voltage is required up to and including 500 MHz.
3/
1,200 volts is at the crest of the audio wave.
4/
Up to 100 watts dissipation is allowable with forced-air cooling of the anode.
5/
For 100 percent modulation including dissipation resulting from power supplied by the modulator.
6/
The maximum instantaneous peak grid voltage for CW ratings shall be within the range of +30 to -400 volts.
7/
Maximum envelope temperature shall be limited to the specified maximum of 300°C under all operating conditions. W here
emphasis is placed on long life and reliability, lower tube envelope temperatures shall be used.
8/
Sufficient conduction or convection cooling shall be provided for all seals to limit temperatures in accordance with 7/. For anode
cooling, an airflow of 12.5 cfm minimum shall be supplied at sea level, and with airflow at 25°C maximum directed with a cowl as
shown on Drawing 157-JAN. W here long life and consistent performance are factors, cooling in excess of minimum requirements
is normally beneficial. Unless otherwise specified, conduction cooling or an airflow of up to 12.5 cfm may be supplied for anode
cooling in all electrical tests involving application of heater voltage.
9/
Group S shall apply, except that it shall be permissible to represent a lot not to exceed one month's production with a sample
consisting of four times the stated (weekly) sample, both for the multiple short life test and the sequential life test.
10/
Test in circuit in accordance with figure 3, or equivalent.
11/
Life test shall be run in a self-excited oscillator cavity.
12/
Each tube shall be subjected to a total of 15 shocks; that is, 5 shocks in each axis X, Z+ and Z- in any sequence as shown on
figure 1.
13/
Other tube contact configurations may be used provided the tube contact area remains unchanged and the socket, jig, or cavity
gives equal performance. Mounting of the jig, socket, or cavity may be at the option of the manufacturer.
14/
Tubes subjected to destructive tests shall not be delivered on the contract or order.
15/
All tests listed under conformance inspection, part 1, are to be performed at the conclusion of the holding period.
16/
Test to be made in cavity in accordance with Drawing 160-JAN. The cavity shall be connected to a standard load with a VSW R
less than 1.5:1. The output coupling from the oscillator and grid or cathode resistor, or both, may be adjusted for maximum power
output.
17/
Airflow through the anode radiator shall be between 3.5 and 4.0 cfm with cowl as shown on Drawing 157-JAN. The grid current
shall be measured at not less than 5 minutes after anode dissipation has been set at 100 watts.
18/
Perform test on 10 tubes selected at random from the first production lot of each calendar year. If more than one tube fails, the test
shall become a part of conformance inspection, part 2, with acceptance level 6.5 and inspection level S3, on all lots in process.
After three consecutive successful submissions, the test shall revert to a 10-tube annual test.
19/
The applied voltage pulse shape shall be measured with noninductive resistor of 1,150 ohms ± 2 percent inserted in place of the
tube. The pulse shape shall be tp = 3.0 µs ± 10 percent, tr = 0.4 µs maximum, tf = 0.7 µs maximum. The pulse repetition rate
shall be adjusted so that Du = 0.0025 ± 5 percent with the above measured pulse length. Test in cavity in accordance with
Drawing 279-JAN. The cavity shall be connected to a load with a VSW R less than 1.5:1. The oscillator output coupling and grid
or cathode resistor may be adjusted for maximum power output.
5
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