Downloaded from https://www.everyspec.com MIL-STD-1311D BAROMETRIC PRESSURE, REDUCED 1. Purpose. The purpose of this test is to detect corona or arcing of electron tubes operated at reduced barometric pressure. Corona and arcing occurs in connection with conducting surfaces which are not enclosed within the evacuated tube envelope. 2. General. Voltage waveform and frequency shall be as specified on the individual TSS. If voltage waveform or frequency is not specified, voltage waveform shall be sinusoidal with F = 48 to 62 Hz. Tube sockets are not required for performance of this test; however, base pin connectors shall not alter corona or arcing characteristics of the tube.
Unless otherwise specified, the sequence of testing shall be as follows: a. Specified voltage shall be applied to tube in test chamber. b. Barometric pressure shall be reduced to the value specified and shall be maintained at that value for a period of 60 seconds. c. With specified voltage maintained, barometric pressure shall be returned to normal. 3. Cathode-ray tubes. This test shall be made with the following voltages applied to all base pins, as applicable. Heater voltage ............................................................................. Nominal rated values Ehk ..............................................................................................
Maximum negative Ecl ............................................................................................... Maximum negative Deflection plate voltages .............................................................. Maximum Eb2 plus maximum ed All other voltages ......................................................................... Maximum rated values. During the test, each deflection plate individually and one at a time shall be switched from +ed (maximum) to -ed (maximum) to +ed (maximum). Corona proof base connectors that do not degrade the tube voltage breakdown characteristics shall be employed.
With voltages applied, the pressure shall be reduced to the specified value and maintained for 60 seconds. Neon light indicators having an approximate 1.0 mA dc sensitivity shall be connected in series with each base electrode for detecting corona or voltage breakdown. The tube shall be considered satisfactory if the neon indicator light does not glow during the 60-second period. 4. Acceptance criteria. Tubes shall show no evidence of corona or arcing. METHOD 1002 METHOD 1002 1002-1 19 April 1968