Oh, one last parameter, please allow for the grids to be strapped to ground
also.
Sorry for the omission.
Mike
----- Original Message -----
From: "k7rdx" <k7rdx@charter.net>
To: "Tom W8JI" <w8ji@w8ji.com>; "Amps" <amps@contesting.com>
Sent: Tuesday, July 18, 2006 10:09 AM
Subject: Re: [Amps] Life and gain of 3-500Z
> The tubes (3-500z`s) were from RF Parts. I replaced (Henry 3K repair
> job)some low hr Eimacs that one had developed a grid to filament short.
Gain
> was compared to a nos pair of Eimac`s.Higher zsac for a given Ep and close
> to 10% more output for a given value of drive.Jim..
> ----- Original Message -----
> From: "Tom W8JI" <w8ji@w8ji.com>
> To: "k7rdx" <k7rdx@charter.net>; "Amps" <amps@contesting.com>
> Sent: Tuesday, July 18, 2006 3:14 AM
> Subject: Life and gain of 3-500Z
>
>
> > > Agreed Tom...My question was why would someone run an amp
> > > with that value of
> > > line voltage if he knew the effect it would have on the
> > > fils.
> >
> > The filament life issue is primarily an issue with good
> > manufacturing quality and steady operation at conservative
> > values.
> >
> > Say you run a tube 24/7/52. In a week you have 168 hours. In
> > a year 8736 hours. There is no thermal cycling. There is no
> > time for the pin seals to get moist and oxidize ruining the
> > glass bond. There are no overtemperature operation or even
> > operation anywhere close to seal rating. The tube is
> > constantly being gettered. All we have is the filament
> > erroding away or losing emission from temperature. Emission
> > life is critical.
> >
> > If we turn the amp on 3 hours a day, transmit 25% of the
> > time with varying power, let the thing sit for a week
> > without use once in a while, and occasionally run the seal
> > temps up to maximum, and use (by force now) poor quality
> > tubes we have a whole different set of likely failures. The
> > data points from and important to commercial service do not
> > apply the same way.
> >
> > >I do know for a
> > > fact that a lot of the Chinese 3-500z tubes have higher
> > > gain than the older
> > > Eimacs
> >
> > I'm not saying that isn't true, but I never saw that happen
> > at the transition time when Eimac went out of the glass
> > power grid business and I started looking at Chinese tubes.
> > I'm not trying to start another long argumentative thread
> > like the tube curve thread, but rather to learn something.
> > How did you measure gain and where did the tubes come from?
> >
> > 73 Tom
> >
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|