Downloaded from https://www.everyspec.com MIL-STD-1311D 3. The operation of the equipment shall be as follows: a. Calibration. The gain shall be adjusted for 50 mW output by removing the tube from the socket and introducing the specified calibrating voltage, at a frequency between 50 and 5,000 Hz into the anode circuit at the tube socket. During calibration, the output of the amplifier shall be terminated in a load resistor having the same impedance as the speaker. The signal and calibrating network shall be removed. b. Test procedure. The TUT shall be inserted.
The tube shall be operated under conditions as specified on the specification sheet in an adapter in accordance with figure 4 of Drawing 194-JAN. When operating under the above conditions, the automatic tapper shall be energized and the average maximum output as observed during approximately six taps noted. If the output reading is rising, continue only until the reading is stabilized. Then, the tube shall be tapped sharply two times with a mallet, using a 2-inch stroke, and the output re-read under automatic-tapping conditions. 4. Rejection.
Tubes shall be rejected for microphonics if the average maximum VU meter readings exceed the limit(s) specified on the TSS either before or after the manual tapping when the output load switch is in the microphonics position. Tubes shall be rejected for noise if any objectionable noise is heard in the speaker such as that caused by leakage, intermittent shorts, etc., when the output load switch is in noise position. Objectionable noise shall be defined as clicks or scratchy noises. METHOD 2201 2201-2 19 April 1968