Eric Moore <emoore@windemullerelectric.com> wrote:
>...The tubes test good, but could they be gassy from sitting all of these
>years? I am not very familiar with 3-500Z's, will letting the filaments
>heat, and just sit there for a few hours, cooking, de-gas the tubes if they
>are gassy?
This is as much a question as an answer, but FWIW:
I know nothing about 3-500Z's, but a close friend and co-worker
successfully degassed quite a few 50-year-old (WW II vintage) 807's and
other relatively small tubes by letting them run with (controlled) plate
current. First he ran them with just their cathodes heated; but nothing
happened. Then he applied B+ (a few hundred volts) and adjusted the grid
bias to set the plate power dissipation to a healthy but safe level -- and
the tubes degassed themselves within a day or two IIRC. Whether this
technique will work with a 3-500Z, I don't know. Perhaps in an 807 the
gettering material is applied to the plate, so it works when the plate is
hot. I have no idea how a 3-500Z is gettered. Is its plate metal? Is the
outside of the plate gray? If so, that might be a getter.
73 de Chuck W1HIS
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