On Sat, 2007-10-13 at 00:34 -0400, Gary Hoffman wrote:
> How does one leave the HV off the tubes ? Do you mean to go in and
> disconnect an HV lead or leads ?
> Or do you mean to turn on the power and not apply any drive for a long time
> ? It would seem awkward to physically disconnect the HV. Then too I have
> read much (rather heated) discussion on-line that says that heaters alone do
> not energize the getter enough to do any good. Comments on this ?
>
The getter is always active, its a reactive metal, on purpose. It does
get warmed above room temperature in most power tubes after hours of
heater or filament operation and if there are gas molecules disturbing
the vacuum there ought to be circulation driven by the heat of the
heater or filament to eventually bounce those molecule off the glass and
other parts and so to impact the getter deposit.
The tube makers have been telling us to run tubes with filament or
heater alone for a day after long storage to clean up the gas and they
have been saying that for longer than I've been alive. It does work. But
a tube with a flashover from being a bit gassy may be destroyed so the
alternative is not good economics.
If the plate (and screen and bias) voltage is not on a separate switch,
then plate caps have to be left off and circuits cut. It may be better
to rig up a tube socket and transformer on the work bench than to use
the radio for that cooking.
73, Jerry, K0CQ
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