tube shields

[EP Swynar]

Hi Dean,

An interesting aside re. tube shields...

There was a piece awhile back ("Electric Radio" magazine...?) where some
analysis was done on the longevity of common tubes with specific shields
attached to them...

If I recall correctly, the ONLY shield that did not reduce tube life due to
over-heating was the black-metal military type...the common bayonet-attached
/ internal spring jobbies were death to tubes, relatively-speaking.

I'm sure someone with a memory better than mine can enlighten us all further
on this...but I guess the bottom line is, for maximum tube life, if you
don't require a tube shield in your circuit(s), DON'T USE ONE.

~73~ Eddy VE3CUI - VE3XZ


**************************************


----- Original Message ----- 
From: "W Dean Milner" <heath at CAISTEAL.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Tuesday, November 13, 2007 11:58 AM
Subject: Re: tube shields


> At 2007-11-12 Monday 22:14 -0500, W5UQ wrote:
>
> >Suggestions:
> >Make sure SHIELD over 6CL6 and shield on driver 6cb6 or 6au6(cant
remember
> >which tube) that shields are scraped and grounded to the ground pin.
Also
> >check the wire that goes through the chassis near the driver tuning
> >varible capacitor.  It can cause "oscillations" sometimes and only on
some
> >bands.  Move it some to make sure it sticks through the chassis "just
like
> >the manual says".
>
> Surprisingly, When I got my SB401/SB301 many years ago there wasn't a tube
> shield to be found in them. Despite that they worked like  a charm. Guess
I
> got lucky. I've long since found some tube shields as appropriate though
> their use has not seemed to make any difference.
>
> 73, Dean
> VE1CBF
> http://www.ve1cbf.ca
>
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