[Amps] Gettering GU-74B's in-place with screen voltage?

[Jim Barber]

Hi Russ,
That seems to be the most common opinion, thanks.

The annoying part is that I gathered all the parts for my DIY HiPot 
tester over a year ago, and never had or took the time to build it. I've 
heard stories that GU-74B emission life can be extended by breaking the 
filaments in gradually, (and that may be true) but what I really need to 
know is if the silly tubes will go 'bang' when I fire the amp up.

I suppose for the money invested I should stop here, order a socket and 
a cheap blower for the gettering fixture, then build the HiPot while I'm 
waiting on the fixture parts. I bought a bundle of 1/2" x 12" x 24" 
clear acrylic with the rest of the HiPot parts, so I s'pose I could use 
that for the gettering fixture box as well. With 50+ CFM of air passing 
through, I doubt the socket would get hot enough to soften the acrylic.

This kind of patience isn't my long suit... Bother. ;-)

Thanks,
Jim N7CXI

On 3/12/2012 7:41 PM, Russ Williams wrote:
> Hi Jim. I would be suggest not running positive screen voltage without
> the plate voltage present. The screen could possibly be ruined by
> drawing excess current. Someone please correct me if I am off base here.
>
> Russ
>
> ------------------------------------------------------------------------
> *From:* Jim Barber <audioguy at q.com>
> *To:* "Amps at contesting.com" <Amps at contesting.com>
> *Sent:* Sunday, March 11, 2012 10:47 PM
> *Subject:* [Amps] Gettering GU-74B's in-place with screen voltage?
>
> Is there any reason I shouldn't getter a set of GU-74B's in-place in the
> amp with blower air, filaments hot, and with grid and screen bias
> applied, but with the plate caps lifted? The amp in question is a QRO
> HF2500DX that appears to be virtually unused, but also appears to have
> been stored for an unknown amount of time.
>
> Most of my experience is with metal-ceramic triodes (which "bang" after
> storage without gettering) and good-old beam pentodes like the 813,
> which don't, or at least haven't yet for me, at least. These (Russian)
> metal-ceramic tetrodes are undiscovered country, so I may be being
> over-cautious. Or not?
>
> Thanks,
> Jim N7CXI
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