Downloaded from https://www.everyspec.com MIL-STD-1311D HEATER-CATHODE LEAKAGE 1. Rated heater voltage. The rated heater voltage shall be applied. For heaters having a rating of less than 35 volts, either ac or dc voltage shall be used; for heaters having a rating of 35 volts or greater, only ac heater voltage shall be used. One hundred volts dc in series with a microammeter shall be applied between the highest numbered heater pin and the cathode. If ac heater-cathode potential is specified, the heater voltage shall be phased to subtract from this heater-cathode potential.
The current shall be determined for both negative and positive polarities between heater and cathode, except for rectifier sections of multiunit tubes, in which the measurements shall be made with the heater at a negative potential with respect to the cathode. The absolute values of the leakage current measured shall not exceed the limit specified. All other tube elements, except those internally connected, shall be electrically isolated from the heater during this test. A resistor, in series with the current meter, of not more than 1,000 ohms per volt of heater-cathode potential, shall be used in this measurement. 2. Voltage drop.
The voltage drop which is developed across a protective resistor is considered in setting up the limit. The stable value of heater-cathode leakage current, when measured under both negative and positive voltage conditions, shall not exceed the limit(s) specified. METHOD 1336 METHOD 1336 1336-1 19 April 1968