10-16-2009, 03:25 PM
Couldn't agree more. Until the filament is open or the vacuum breeched, there's always hope for an old tube. I have had some limited success in running a tube for a while with above normal filament voltage until the getter absorbs gas. This I do on my Hickok 539 tester. I'm not talking about ancient thorium coated filaments, but more "modern" types. I know this is not supposed to work, but sometimes it does.
And microphonic tubes may function just wonderfully in other roles other than audio. And even dual heater tubes with one filament gone might be OK where you only need half a tube to get the job done.
In any case I do try to save the tube base on any duds, and can build adaptors to use whatever else I have on hand in the way of tubes and sockets to make a sub without changing the original chassis. (I.E. you can make a 35W4 sub for the 35Z5.)
And microphonic tubes may function just wonderfully in other roles other than audio. And even dual heater tubes with one filament gone might be OK where you only need half a tube to get the job done.
In any case I do try to save the tube base on any duds, and can build adaptors to use whatever else I have on hand in the way of tubes and sockets to make a sub without changing the original chassis. (I.E. you can make a 35W4 sub for the 35Z5.)
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