|[AMRadio] 813 question|
w5omr at satx.rr.com
Tue Jan 31 15:02:57 EST 2006
Jim Wilhite wrote:
> Don't know about the Russian tubes, but tubes shipped from Eimac had
> an instruction insert that said to burn in the tubes before applying
> Since there is no such thing as a perfect vacuum a small amount of gas
> is left in a tube. That is the purpose of the getter, to absorb those
> gasses. If I were installing a very old tube, say a 304 TL or 250TH or
> high power tube in a circuit, I would burn it in for at least an
> hour. As I recall the instructions for the 4-X series of tubes called
> for about 30 minutes.
One of the 'ebay special' 250TH's I got, claimed to be NIB... after
30mins with the filaments on it, I hit the grid drive on the tube, and
it turned blue inside, like an 866.
If that's the case, in the larger tubes, I'm think there needs to be
-more- time for 'burn-in'. 30 mins didn't get it, for me.
Then again, the base wasn't loose, either, after 30 years of sitting
73 = Best Regards,
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