RE: [R-390] Tube shields? We don't need any stinking tube shields!

[Jim M.]

The original purpose of the shields may have been to hold the tubes in place
during rough transportation.  The military has some tough drop, shock and
vibration specs. and tests to pass.   The design of the shields may have
evolved to try to keep temperature down to the "bare tube" level while still
having a restraining shield in place.

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Les Locklear
Sent: Monday, December 03, 2007 5:29 PM
To: r-390 at mailman.qth.net; Hammarlund at mailman.qth.net
Subject: Re: [R-390] Tube shields? We don’t need any stinking tube shields!

I should have noted that immediately after shooting the tube shield 
temperature, the shield was removed and the tube temperature was shot.

Les
----- Original Message ----- 
From: "Les Locklear" <leslocklear at cableone.net>
To: <r-390 at mailman.qth.net>; <Hammarlund at mailman.qth.net>
Sent: Monday, December 03, 2007 4:09 PM
Subject: [R-390] Tube shields? We don’t need any stinking tube shields!


> Groups,
>
>
>
> This test was done using a Raytek laser digital thermometer. Temperatures 
> were taken from a 6BZ6 1st RF amp tube on a John R. Leary SP-600JX no 
> suffix number, serial number 1262. Ambient room temperature was 75°F. I’m 
> not a scientist nor should this be misconstrued as a scientific test. I 
> have always been curious as to whether the IERC tube shields “actually” 
> prolong tube life. As noted there were several different tube shields used

> in this “test.” Also note there are several different types of inserts 
> inside these tube shields.
>
>
>
> The “Real McCoy” IERC Tube Shields have a finger grip type of insert that 
> acts as a heat sink and the test results show that the temperature 
> difference between the shield and the tube itself is little. That should 
> tell us that that type of shield is the “Standard.” For your information, 
> I don’t use tube shields and my tubes seem to last a long time.
>
>
>
> Take this information as it’s meant to be, strictly informational.
>
>
>
>
>
>
>
>  1.. Shiny metal Eby tube shield no insert. 94°, bare tube 124°F.
>
>
>  2.. Shiny metal Eby tube shield with seven-sided black aluminum insert. 
> 96°F, bare tube 127°F.
>
>
>  3.. Dull metal Elco tube shield no insert.108°F, bare tube 135°F.
>
>
>  4.. Black heat resistant painted Eby tube shield no insert. 104°F, 126°F 
> bare tube.
>
>
>  5.. Black anodized Eby tube shield with “waveform, nine ridges” aluminum 
> black heat shield insert. 107°F, bare tube 127°F.
>
>
>  6.. Collins black anodized tube shield with “waveform, nine ridges” 
> aluminum black heat shield. 100°F, bare tube 122°F.
>
>
>  7.. W.P.M. tube shield with five-sided aluminum insert. 106°F, bare tube 
> 118°F.
>
>
>  8.. IERC tube shield with “finger grip” type beryllium insert. “The 
> Standard.” 102°F, bare tube 104°F. ( has to be the insert)
>
>
>  9.. Bare tube, no shield. 6BZ6 114°F.
>   YMMV
>
>
> Les Locklear
> Gulfport, Ms.
> DX'ing Since '57
> http://www.hammarlund.info/
>
>
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