After reading the info here in AMPS about Conditioning
Tubes, I have a few questions:
Upon receipt of a set NOS or Medical pulls , how should
the average Ham with limited test equipment test the tubes
before placing them in the amplifier?>>
1.) Ceramic tubes with small sensitive grids should always
be used with enough anode resistance (resistance rated at
high enough voltage) to prevent damaging the grid during a
fault.
2.) The amplifier should also always have a fast electronic
grid disconnect to prevent damaging the grid from RF
generated grid current. A warning light or fuse won't do.
If you have that, you can really just plug them in. I would,
if they had been unused for a while, run the filaments for a
period of time before applying high voltage. External anode
tubes degass from cathode heat.
<< I am thought that maybe an Ohmeter should be used to
first test the tubes for shorts, grid to filament and then
maybe a 220 Variac connected to the Amplifier AC Input lines
. But I am not sure of the voltages or timing to condition
the tubes? >>
The quickest way to ruin an oxide cathode tube is to run it
at low heater voltage while drawing current. They also do
not degass by anode heat, although they might degass by a
controlled arc.
<< 2. If the tubes work OK, and the original tubes are put
back, what would be a reasonable time to rotate the Med
Pulls or the NOS tubes purchased as spares? I have read that
the tubes need to used occasionally to burn off any air that
may have been leaked into the tube?>>
Generally only larger glass tubes have that problem.
73 Tom
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