measures wrote:
>
>>
>>measures wrote:
>>>? I have tested many metal anode-cooler 3-500Z tubes that g/fil. shorted
>>>after a big-bang. The majority had under 3uA of grid/anode leakage at
>>>8000v. The subsequent autopsies revealed no arc marks on the grid.
>>
>>The reasons for observing low gas currents if you delay more than a few
>>seconds after the event have been explained many times - "it's the
>>gettering action".
>>
>In almost all cases, the mains breaker or mains fuses opened at the
>big-bang. .
>
>>Does testing 3-500Zs cause amnesia?
>>
>Gettering in cold 3-500Z's?. Only in the Rauchian world.
If there is a chemically active surface (hot anode), gettering in a tube
the size of a 3-500Z occurs on a timescale of seconds.
It only takes a very small release of trapped gas impurities to trigger
an arc. If the tube was running and the anode was hot, that gas will be
mopped up again before the anode cools. By the time you can get the tube
to a hi-pot tester, the gas will probably be long gone.
But you've been told that several times before: hence my comment about
amnesia.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.com/g3sek
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