If they are not 4-400As, tetrodes, (which can be used as grounded grid triodes,
plug in replacemets for the 3-500Z. in a pinch.) Will not put out the same RF
without circuit changes.....they are identical look alikes.
I think each, or at least one, of the grids are connected to muiltiple pins, in
which you can test with an ohmmeter.
Also, if you put the tubes in the refrigerator cool them down, then bring them
back in
a room temp environment, sometimes the condensation will bring out the tube
type printing, even if you cannot otherwise see it.
Best Regards,
Pat Barthelow; Echoes of Apollo
> Date: Sun, 28 Nov 2010 20:22:26 -1000
> From: ken.d.brown@hawaiiantel.net
> To: mike9v@gmail.com
> CC: amps@contesting.com
> Subject: Re: [Amps] Help identifying tubes
>
> They are definitely not 3-500 or 3-400, because those don't have the
> metal bases. 4-250 don't have fins on the anodes, so would have to be
> 4-400, unless it is a pentode. You could probably figure that out with
> an ohm meter and the data from Eimac (or descendant) site.
> > Hi Guys
> >
> > Someone gave me 2 tubes years ago and said they were 3-500s. Well I am not
> > sure they really knew, and I don't know as the lettering is worn off. Here
> > is a link with some pics.
> >
> >
>
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