I was speaking to a friend the other day about amps in general and then by
accident we hit on the fact that in some amatuer amps made with GU74b
valves, the valve lies in a horizontal, and not vertical position. He argued
that according to some sources this is bad as the various "pollutants" that
fall off the anode, rather than falling to the base of the tube (as it was
designed?) all onto the grid, which eventally cause a short circuit in the
valve.
>
Any comments?
>
Richard, SO5GB
Warsaw
> ----- Original Message -----
> From: "Phil Clements" <philk5pc@tyler.net>
> To: <RFlabnotes@aol.com>; <amps@contesting.com>
> Sent: Saturday, January 17, 2004 12:30 AM
> Subject: Re: [Amps] Power-off tube cooling
>
>
> > Subject: [Amps] Power-off tube cooling
> >
> >
> > > I am curious about the origin of this mythology. It would
> > be nice to see some
> > > factual data, or, at least, logic to support it. (snip)
> > >
> > >> Is there really some good physics to rely on here, or is
> > this just another
> > > piece of folklore that won't go away?
> >
> > Assuming you have a tube large enough and hot enough to
> > warrant cooling after power-down, the idea is to force the
> > residual hot air up and out the chimney instead of into
> > other components on and under the chassis. This is about a
> > $50 addition to an amp; one has to weigh the cost against
> > the protection provided to tank components that may suffer
> > long-term damage. Since many large amps I have seen do have
> > this feature, I can only assume the cool-down feature is
> > prudent in those cases.
> >
> > (((73)))
> > Phil, K5PC
> >
> >
> >
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
>
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