On Sep 24, 2006, at 1:56 PM, craxd wrote:
Jim,
Did you ever get to speak to anyone at Eimac about where the getters
were at in a 3-500Z?
My take on gettering / gas contamination, or the lack thereof, is that it mainly came from a station who was trying to explain big-bang arcing in the output sections of HF/MF amplifiers by a means other than by an intermittent VHF parasite. However, since an arc in a near- vacuum is nearly silent acoustically-speaking, his internal-gas explanation of big-bang arcs did not wash. Other problems with his explanation is that tubes removed from amplifiers that sustained a big-bang arc typically show a normal vacuum on a high-potential tester, and that the VHF suppressor resistors from such amplifiers are often considerably higher in resistance than the marked value -- thereby suggesting the reason he didn't want.
That's a question I'd say a few of us would like
to find out about as I think there is some erroneous info floating
around on the net about it. One said it was the anode itself, but it
doesn't get hot enough in my opinion to do it,
Agreed, which is probably why the secret Admonishtrator (sic) bristled at your posts about this fly in his pie.
and would actually have
relaeased hydrogen gas if, a certain gettering material were applied
to it. Any thoughts on this?
73,
Will
--- In ham_amplifiers@..., "pentalab" <jim.thomson@...>
wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
Do getters stop working when the HV is applied? ... when the
drive is applied? ... or when both are applied?
### getter's [per Eimac and Svetlana] are ALWAYS working...
as long as the fil is lit. HV + drive are not part of the
overall process.
ANY and
all residual gas and junk is absorbed by the getter's... and
you will never get any surprises... like any arcing from
anode to the grounded grid !!
I've fired up several gassy tubes, the insides glowed blue, but
none of them arced to the grid.
### Are u talking about 3-500Z's and 4-1000's ???? [glass
tubes] I have had new 4-1000's that glowed blue. It was
not gas either.... it was an anomoly/defect in the glass....per
Eimac. The glass would glow blue.... only when drive applied.
### Then I have also seen 4-1000's that glowed blue INSIDE the
anode/screen/grid compartment..... dunno if that was with drive
applied or not...... that was too long ago.
### With a big ceramic triode/terode.... I highly suspect... If
it's gassy... and BOTH HV and drive are applied.... arcs MIGHT
occur between anode to screen... or anode to grid.
### If the vac isn't good and hard in the 1st place.... that
could easily create even more problems.
### I had several 4-1000's yrs ago... that looked like a smoke
bomb going off inside.... when the fil V was applied!! They had
either a lousy vac.... or..'had gone to air'.
### did u ever see a blue glow inside the ceramic portion of a
metal tube ?? Kinda tough to see..with the chimney on.
### All I was trying to get at was.... if 16 guys say to use
48 hrs to getter a new/rebuilt tube.... and anything less is
gonna be a problem... cuz they have tried many diff time
frames... who am I to argue?
### Svetlana claims their tubes are proccesed at a higher temp
than Eimac [during the construction of the tube]... one would
think the Svetlana tubes would have less of a 'gas' problem
than an Eimac ?
### The Svetlana tubes all use a 'spiral mesh fil' and
where all the mesh criss crosses... they are welded. ... so
u don't wanna slam the fil V on.. it can buckle the mesh fil
sideways..esp with over rated fil xfmrs [eg: I use a 80 A
rated fil xfmr on my 50 A rated 3000A7]......... another reason
to step start em.
## I don't have the time or patience to inadvertantly destroy
expensive new/rebuilt tubes.
Later... Jim VE7RF
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