MIL-PRF-1/1660C
TABLE I. Testing and inspection - Continued.
12/ The tube shall be mounted in socket in accordance with Drawing 276-JAN and vibrated with simple harmonic motion. The
peak acceleration over the frequency range shall be within ± 20 percent of the reference acceleration at 100 Hz. The
frequency shall vary from 55 to 500 Hz and return to 55 Hz with approximately logarithmic progression and shall require
4 minutes minimum, 6 minutes maximum to traverse the range. Each tube shall be vibrated for 30 minutes in each axis -X and
+Z as shown on figure 1, except that if the cumulative result of test on 50 or more tubes of a construction show that more than
75 percent of the tubes have higher output voltage in one axis, subsequent measurements need to be taken only in the axis
giving the higher reading. The voltages specified herein shall be applied to the tube during vibration. The value of the
alternative voltage, Ep, produced across the resistor, Rp, as a result of vibration shall be measured with a suitable device. This
device shall have an appropriate voltage range, shall have the ability to measure, with an error of less than 10 percent, the rms
value of a sine wave of voltage at all frequencies from 20 to 20,000 Hz. The value of the vibration output Ep, shall not exceed
the limit specified herein at any point in the sweep frequency range during the last complete cycle of cycling vibration.
13/ This test shall be performed during initial production and then annually thereafter. An accept on zero defect sampling plan
shall be used, with sample of three tubes with an acceptance number of zero failures. In the event of failure, the test will be
made as a part of conformance inspection, part 2, acceptance level 6.5 (see 21/). The annual sampling plan shall be
reinstated after three consecutive samples have been accepted.
14/ Torque test shall be performed as follows:
a. The tube shall be held securely at the cathode connection. A force of 5 inch-pounds shall be applied to the heater cup
without perceptible shock. This test may be made by applying the force at right angles to the inside of the cup at a point
0.109 ± 0.016 inch from the cathode end of the tube. An approved equivalent method may be used. The heater cup shall
not loosen or short circuit on the cathode connection. This part of the test shall not be required if the space between the
heater cup and the cathode sleeve is completely filled with insulating material.
b. A torque of 15 inch-pounds shall be applied between anode and cathode without shock.
c. A torque of 40 inch-pounds shall be applied between anode and grid without shock.
15/ Test in jig in accordance with Drawing 280-JAN. Each tube shall be subjected to a total of 15 shocks; that is, 5 shocks in each
axis, +Y, +Z, and -Z, in any sequence, as shown on figure 1.
16/ At zero hours of life test, establish the drive conditions necessary to obtain a peak anode current of 3a (minimum) with an
anode voltage of 1,000 V dc and a bias of -40 V dc. The pulse width of the modulator shall be 2 µs (minimum) and the duty
cycle shall be 0.0025 (maximum). W ith the drive level determined at zero hours, check the anode current at the end of life.
Maximum allowable drop in anode current shall be 25 percent.
17/ The applied voltage pulse shape shall be measured with a 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 heater contact of the cavity may be lengthened as required and the anode flange "M" removed to attain
proper oscillation. The cavity shall be connected to a load and a VSW R of less than 1.5. The oscillator output coupling and
the grid or cathode resistor may be adjusted for maximum power output.
18/ Test shall be conducted in power amplifier cavity as shown on figure 4. Driving power is defined as the net power delivered to
the amplifier cavity input terminals and the reflected power shall be subtracted from the incident power to obtain the net driving
power. The output tuning shall be adjusted for maximum power output.
19/ Test is to be made in cavity in accordance with Drawing 160-JAN. The position of the cathode line and the heater contact are
changed to permit proper contact as required by the tube dimensions. The anode flange "M" may be removed to obtain proper
oscillation. The cavity shall be connected to a standard load with a VSW R of less than 1.5. The output coupling from the
oscillator and grid or cathode resistor or both may be adjusted for maximum power output.
20/ Test tubes in circuit in accordance with figure 5, or equivalent.
21/ This specification sheet uses accept on zero defect sampling plan in accordance with MIL-PRF-1, table III.
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