Tube labeling and age and getter

[Craig Maier]

Sometimes, you will come across tubes that have "JAN" above the tube number. This indicates that it was approved for military usage standing for Joint Army Navy. Many of these can be purchased as "NOS" which means New Old Stock. Buyer beware - - - most of these really are new but never used, but sometimes they may be "Pulls" from old electronic equipment, so emissions or trans-conductance may not be up to their original specifications but may still work in your vintage or diy tube based equipment.

Craig

ps - the purpose of the Getter is to maintain a high lever of vacuum with in the tube envelope.

[Craig Maier]

The getter on the inside glass of an electron tube should be silver-ish in color. If it beginning to fail to perform its function, the edges of the getter color will begin to turn to a brownish-red color. This process will progress until the entire getter area will ultimately turn to white and the tube will fail to perform to specs.

Craig