Downloaded from https://www.everyspec.com MIL-STD-1311D METHOD 1211 INSULATION OF ELECTRODES Test each control grid to all other elements tied and test each anode to all other elements tied. In the test set, the center tap or one side of the filament transformer shall be tied to the positive bus. When testing multisection tubes, all elements of sections not under test shall be connected to the positive bus. The value of the insulation resistance, measured with the applied potential specified in 1, 2, 3, and 4 below as applicable, shall be not less than 100 megohms for reliable tubes and not less than 10 megohms for all other receiving tubes.
This test shall be performed with the filament energized immediately after the other specified electrical tests are concluded or immediately following a minimum pre-heating time of 5 minutes. 1. Receiving tubes with a maximum anode potential rating greater than 330 V dc. Receiving tubes with maximum anode potential rating greater than 330 V dc, or rectifiers whose maximum rms test voltage per anode exceeds 300 V ac, shall be tested with a negative potential of at least 500 V dc when measuring insulation resistance from anode to all other elements tied. The applied potential shall be not less than -300 V dc when measuring resistance from each control grid to all other elements tied. 2.
Receiving tubes with maximum anode potential rating of 330 V dc or less. Receiving tubes with a maximum anode potential rating equal to or less than 330 V dc, except those intended for dry-battery operation, or rectifiers whose maximum rms test voltage per anode is less than 300 V ac, shall be tested with a negative potential of at least 300 V dc when measuring insulation resistance from anode to all other elements tied; however, the applied potential shall be a negative voltage of at least 100 V dc when measuring insulation resistance from each control grid to all other elements tied. 3. Receiving tubes intended for dry-battery operation.
Receiving tubes intended for dry-battery operation shall be tested with a negative potential of 100 V dc. 4. For tubes other than receiving, the value of insulation resistance and the applicable voltages shall be specified on the TSS. METHOD 1211 1211-1 19 April 1968