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Tube envelope size variation with heat / cold
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Author:  thehoj [ 20 Jul 2015, 18:42 ]
Post subject:  Tube envelope size variation with heat / cold

I thought this was going to be an easy one to find the answer to, but I can't seem to find the answer.

Does the envelope on a vacuum tube change size when it heats up? Even a small variation?

I'm looking at mounting a tube slightly through the top of an aluminum plate, and so I want to know how much air space needs to be around the envelope.

Author:  Suncalc [ 20 Jul 2015, 19:21 ]
Post subject:  Re: Tube envelope size variation with heat / cold

There has to be enough room for air to flow around the tube. Think 1/8" minimum for a signal tube and a minimum of 1/4" to 3/8" inch for a power tube. I split the definition by overall power dissipation (heater + plate) at about 2-1/2 watts. YMMV.

Warning: Metal close to a vacuum tube can get HOT! Make appropriate design accomidations.

Author:  gofar99 [ 20 Jul 2015, 20:43 ]
Post subject:  Re: Tube envelope size variation with heat / cold

I agree and use similar spacings. Additionally you may want to be sure the tubes themselves are spaced apart. I like to use about one diameter of the tube separation between tubes. More is better.

Good listening
Bruce

Author:  thehoj [ 20 Jul 2015, 23:15 ]
Post subject:  Re: Tube envelope size variation with heat / cold

Thanks guys.

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