"Chuck Harris" wrote in message
...
terry wrote:

2) It MIGHT be possible to get rid of gas in a tube by reheating the
getter; there might be active 'getting' material left? No expert on
tube manufacture but understand those getters were heated by RF. So
could be done again?

You can heat them again, but it will be to no good purpose. The getter
is a tray filled with a getter metal, such as barium. The tray is usually
in the shape of a loop so that it is easy to induce RF current into the
loop
and heat it very hot. The metal all evaporates and deposits on the cool
glass (usually) It is very unlikely that there is anything left over.

With there now being a spot of getter metal on the glass in the vicinity of
the getter loop, I'd think that applying intense RF energy to the area would
also heat that spot (the way silvered or gilded patterns on a china plate,
or even more dramatically the coating on a CD, heat up and spark in a
microwave oven). Assuming this heat was enough to re-vaporize part of the
spot, and the glass didn't break from the thermal shock, I'd wonder if the
vaporized metal might capture enough extra air in a slowly leaking tube to
make a difference for a short time.

HiTech RedNeck wrote:


With there now being a spot of getter metal on the glass in the vicinity of
the getter loop, I'd think that applying intense RF energy to the area would
also heat that spot (the way silvered or gilded patterns on a china plate,
or even more dramatically the coating on a CD, heat up and spark in a
microwave oven). Assuming this heat was enough to re-vaporize part of the
spot, and the glass didn't break from the thermal shock, I'd wonder if the
vaporized metal might capture enough extra air in a slowly leaking tube to
make a difference for a short time.

Re-heating the getter flash might work, but it also might release all of the
gases the getter trapped on the first go around. It depends on what happens
when you heat barium oxide, barium nitride, barium hydride, ... along with the
barium metal, to a few thousand degrees F in a vacuum.

And, the getter does nothing towards trapping helium that diffused through
the glass... though that shouldn't be too much of a problem, as helium is
rather scarce in our atmosphere.

-Chuck

HiTech RedNeck wrote:
With there now being a spot of getter metal on the glass in the vicinity of
the getter loop, I'd think that applying intense RF energy to the area would
also heat that spot (the way silvered or gilded patterns on a china plate,
or even more dramatically the coating on a CD, heat up and spark in a
microwave oven). Assuming this heat was enough to re-vaporize part of the
spot, and the glass didn't break from the thermal shock, I'd wonder if the
vaporized metal might capture enough extra air in a slowly leaking tube to
make a difference for a short time.

Remember, it's a reactive metal. When it's worn out, it's worn out because
it's oxidized. Reheating it won't do any good; you have to get the oxygen
out of the tube. At best, reheating will boil off the oxygen and fill the
tube back up with it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."