On 7/24/06 at 6:25 AM R L Measures wrote:
>On Jul 23, 2006, at 10:40 PM, Peter Chadwick wrote:
>
>> Rich said:
>>
>> >I autopsy tubes, and I have no yet seen an arc mark in a kaput tube
>> with a good vacuum.<
>>
>> It's sad that G6JP is no longer alive. He spent his entire working
>> life doing tube manufacture and applications at the M-O valve
>> company, and he said that flashovers weren't uncommon.
>
>Surely, and those valves that had leaky seals and flashed over, did
>not pass final test, landed in the recycling bin, and never saw
>daylight.
>> There's also the articles in the Journal of the IEE. My father in
>> law tells me that they had flashovers in continously pumped tubes
>> at the QRO point to point stations he worked at -although the
>> biggest problem was when someone with greasy fingers touched the
>> grid during re-assembly. That meant that they had a lot of pumping
>> to do before the valve really got hard.
>>
>> So Mr. Measures, the fact you've never seen what you take to be
>> marks of a flashover in a tube with good vacuum doesn't mean that
>> it doesn't occur.
>Agreed. However, there's presently a faint smell of specious
>reasoning in the air.
>> But, of course, proving (or disproving) a negative is not easy, so
>> either party can sit back in the warm glow of satisfaction that
>> really, they're the ones who are right!
>
>Are Au and Mo notable emitters?
>Can the grid of a tube with a hard vacuum reach high temperatures if
>no current is passing through it?
>If zirconium has to be at 1400ºC (Terman) in order to absorb oxygen
>and nitrogen, how can a 3-500Z's anode getter air molecules?
One needs to study how tubes are constructed to see what may happen. The metals
used in them were picked
over their high heat qualities (wouldn't melt). The plating had to do with
emission of electrons.
Yes, I seen a reference earlier about the 3-500Z having a getter of zirconium.
For it to work, it's optimum temp is
1400 deg C and is what it's ran at in this application. In that case, the anode
would be white hot (the welding color of steel). There's some other problems
with this too, but I won't go into them here (IE Hydrogen gas). If one actually
wanted to make this work, it looks like a tantulum anode would have been a
better choice.
>
>Editorial -- As I see it, the proponents of the floating grid
>catastrophe theorem have a conflict between reality and what they
>wish reality to be.
The theory is what has me bothered in that, if I read them right, think a grid
could become positive from an arc. Also, in the ways a grid could become
positive. A good read of the book, Radio Engineers Handbook, by Terman will
straighten out all the mis-conceptions. Actually, Tubes 201 follows right along
with it.
>
>cheers, Peter
>> 73
>>
>> Peter G3RZP
>
>R L MEASURES, AG6K. 805-386-3734
>r@somis.org
Best,
Will
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|