In article ,
Sam Goldwasser wrote:
First check for continuity of the filaments. Often, the open and that's
a simple test!

Yup. Open filaments are a show stopper all right.

These tubes all have good filaments but are old enough that
some, probably most of the cathodes, are depleted from use.
--

Martin McCormick WB5AGZ Stillwater, OK
Information Technology Division Network Operations Group