[AMPS] Sucking instead of Blowing

[2]

>
>Hello all
>
>I've been off this reflector for a few weeks - hope my
>comments are relevant to this cooling discussion.
>I have a homebrew amp. with a single QY5-500
>(looks a bit like a large 3-500z) which is cooled by
>a side-mounted fan - there is a definite difference
>in temp. between the side of the valve nearest to the
>fan and the side furthest away.  

€  Greetings, Chris
    1.  how did you measure these temperatures?
    2.  does your amplifier use a split chassis?
    3.  how tall is the tube?
    4.  what is the diameter of the fan?
cheers

> If I was rebuilding this
>amp. I would use a fan blowing up from below + a
>glass chimney, or some better method.
>
>However, I was under the impression that most of
>the heat given off by e.g. 3-500Z-type valves is in
>the form of infra-red radiation from the anode structure,
>a proportion of which will be absorbed by the glass/
>quartz envelope and raises the temperature of this
>envelope.     Some valves seem better at allowing this
>infra-red to pass through and heat the surrounding
>metalwork etc, than others.
>
>In the Ameritron AL-80 (single 3-500ZG) I have, the metal
>case gets very warm after a relatively short time of use,
>and takes about 10-15 minutes of cooling without
>transmitting to return to room temperature.  I suspect
>that the 3-500ZG has cooled down much quicker than
>the metalwork.
>
>What's the point I'm trying to make? - just that it seems
>to be the valve seals that are the crucial area for 
>cooling, and that blasting air at the glass envelope
>isn't really achieving much - yes the glass envelope
>needs some cooling, but why are the insides of the
>P.A. compartment in these amps. not painted matt
>black ?
>
>73
>Chris    GM3WOJ
>
>
>
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>


-  R. L. Measures, 805.386.3734, www.vcnet.com/measures.  
end


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