[Tube-Swap] 3-500z

[Michael Melland, W9WIS]

>Is a burn in time needed on a new  3-500?

>From the RF Parts web page:

TUBE BURN IN
Transmitting tubes generally require a "burn in" time to increase emission
to its nominal value. In broadcast stations, 100-200 hours at rated filament
voltage is allowed for burn in. This initial operation allows the getters,
materials which absorb and hold residual gas, to finish the vacuum of the
tube in its final operating environment. In an Amateur Radio amplifier,
tubes will often require 50-200 hours of "key down" transmit time to remove
the residual gas and condition the filament for full emission. It is well
advised to allow tubes to operate in standby mode (filaments on, no
transmit) for 10 hours before tune-up.

The 811A, 572B, 3-500Z, 4-400, etc. utilize a thoriated tungsten filament,
which is highly dependent upon sufficient filament temperature to provide
adequate electron emission for normal operation. Emission increases as the
thorium migrates towards the surface of the filament wire. This is why it is
recommended to "burn in" these tubes before operation


73 de Mike, W9WIS