Re: [Hammarlund] Re: Tube shields? We don’t need any stinking tube shields!

[jeremy-ca]

A small CPU fan can move sufficient air to reduce the ambient temperature in 
many BA's. Use several if necessary and Velcro wherever they fit. Take the 
5VDC from a filament circuit, rectify, filter and drop the voltage a bit if 
the noise is objectionable. Fans removed from obsolete or defective 
motherboards are freebies. I use Pentium I and II fans.

My 390A is very happy this way as are several other BA's

Carl
KM1H


----- Original Message ----- 
From: "Les Locklear" <leslocklear at cableone.net>
To: "rbethman" <rbethman at comcast.net>
Cc: <r-390 at mailman.qth.net>; <Hammarlund at mailman.qth.net>
Sent: Monday, December 03, 2007 5:46 PM
Subject: [Hammarlund] Re: Tube shields? We don’t need any stinking tube 
shields!


> If I had a bunch of the "Real" IERC shields, I would use them, but I'm not 
> about to pay the price they seem to sell for these days. No shields seems 
> to work for me.
>
> Les
> ----- Original Message ----- 
> From: "rbethman" <rbethman at comcast.net>
> To: "Les Locklear" <leslocklear at cableone.net>
> Cc: <r-390 at mailman.qth.net>; <Hammarlund at mailman.qth.net>
> Sent: Monday, December 03, 2007 4:40 PM
> Subject: Re: Tube shields? We don’t need any stinking tube shields!
>
>
>> Les,
>>
>> While I do not have the sophisticated temperature measuring capabilities, 
>> I have long suspected that the results you've posted was the case.
>>
>> I long done away with those pesky shields, both in R-390As and SP-600s.
>>
>> They DO seem to run cooler!
>>
>> Bob - N0DGN
>>
>> Les Locklear wrote:
>>> 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.
>>>
>>
>>
>> -- 
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>>
>>
>
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