[R-390] Black Tube Shields, IERC

[Jim]

Interesting results.
Has anyone tried painting the silver cam-lock tube shields with black paint?
BBQ flat black paint should work, but is it worth it?

Jim

>A few years ago I went through the process of measuring envelope
> temperatures on a wide range of tubes in a SP-600 with different tube
> shields. It did turn out that the black IERC tube shields did make a
> difference in envelope temperature.
>
> Generally speaking I was seeing 20-60 degrees F difference across the 
> range
> of shields. I had tested with the following;
>
> Factory default, silver cam-lock tube shields with the loading spring to
> keep the tube down it the socket
>
> No shield at all, just using ambient air and radiative cooling from the
> tubes.
>
> IERC tube shields
>
> IERC tube shields with a dab of thermally conductive paste applied to the
> finger-stock grippies inside of the IERC shield (to improve thermal
> conduction between the envelope and the shield).
>
> I had strictly controlled air-flow and room temperature and would let the
> radio stabilize for an entire day before making measurements. This was 
> also
> in a room where I was not moving around in so there was a bare minimum of
> air movement. Room temperature was at 70 F. I measured temperature with an
> optical pyrometer and had put a dab of flat black paint on the top of the
> tube (so I could get consistent temperature readings without gluing
> thermocouples everywhere).
>
> By far the worst was the silver tube shields. If anything these kept the
> heat on the envelope with some temperatures well above 250 F
>
> When I used the IERC's I could get the temperatures in the 150 to 160 
> range.
> If I used the thermal paste it would knock the temperature down another 
> 5-10
> F on average.
>
> Interestingly the chassis temperature went up when using the IERC shields
> due to the mechanical connection at the base of the IERC shield and the
> radiative cooling off of the shields. If you have a concern about 
> capacitor/
> resistor aging this may offset your worries about tube temperatures.
>
> In every instance, the use of a small computer-fan to move air across the
> chassis really helped out in lowering the temperature of the tubes and the
> chassis. This does not need to be a gigantic fan.
>
> If someone was really interested I could drege up my notes and put them 
> into
> a human-readable format. At the time I was doing my little experiment to
> justify the cost of the IERC shields. (I did end up finding IERC shields 
> for
> every tube operated device I have)
>
> -- 
> Ms. Tisha Hayes
>
> ----------------
> "I will not recant the truth. I am corn, not chaff; I will not be blown 
> away
> with the wind or burst by the flail. I will survive both."
> -Walter Milne, 1558
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