[Milsurplus] DIY Vacuum Chamber

[Michael Veach]

I am building a unit to do just that, but not with oil. I am using varnish, probably glyptal or any electrical varnish that is thinned by heat. 
"Imagination is more important than knowledge." Albert Einstein. 

     On Tuesday, September 22, 2026 at 01:35:16 PM EDT, Brenda Gentry via Milsurplus <milsurplus at mailman.qth.net> wrote:  
 
   
The paint pot would be more likely to have a gasket that would seal both pressure  and vacuum. A compressor from a refrigerator, freezer, or dehumidifier will work well as a vacuum pump to keep the costs down. I doubt vacuum would harm an unsealed transformer  or a motor. Some Tektronix oscilloscopes have a high voltage transformer that absorbs moisture and fails until it is heated and dried out. I am wondering if putting it in a vacuum chamber covered with a dielectric oil, heating it, and then drawing and relieving the vacuum a couple times would draw out the moisture and impregnate the coils with the oil and keep moisture out. 
 
    B. Gentry, KA2IVY
 
 

 
 

 
 

 
 

 
 

 
 

 
 

 
 
 Hi 
  If you head over and get a “paint pot” at the big box store, they are good to at least 50 PSI. They also come in bigger sizes (for more money …. how odd … :) ). 
  Same deal, works with pressure or vacuum. 
  If yo want to go “one step up” get a good vacuum pump and put a heat pad under the whole rig.  Things will get *very* dry. 
  One side note: With any vacuum approach fancy or simple: you also will find out if anything in  the radio is “unhappy at altitude” …. not 100% sure that is the sort of research I would dive into. 
  Bob
 
 
 On Sep 22, 2026, at 3:14 AM, Jim Whartenby via Milsurplus <milsurplus at mailman.qth.net> wrote: 
  When a pressure cooker is cooking, it has about 15psi on the inside pushing out.  When used as a vacuum chamber, the 15psi is on the outside pushing in.  Evidently, the aluminum container can't tell the difference!  <grin> Jim 
   Logic is a systematic method of coming to the wrong conclusion with confidence.  Murphy  
  
  On Monday, September 21, 2026 at 04:50:31 PM CDT, Facility 406 <facility_406 at bruteforcedevelopment.com> wrote: 
 
  On 9/21/2026 13:19, Jim Whartenby via Milsurplus wrote:
  > One way to easily remove water vapor is with a vacuum.  One can easily 
  > convert an old pressure cooker into a vacuum chamber for perhaps under 
  > $30 if you already have a hobby compressor / vacuum pump.  The holes in 
  > the cover are national pipe threads so just remove the old hardware and 
  > substitute a vacuum gauge, ball valve and a tubing adaptor along with a 
  > new gasket seal.  Plug any unneeded holes with the appropriate NPT 
  > plug.  I use a small Gast air compressor / vacuum pump with good 
  > results.  This example will hold a decent vacuum for well over a week.
  
  I've thought of that in the past, but have been worried of the bottom 
  imploding.
  
  One idea I had was to bolt an Al plate to the bottom, something maybe 
  3/8" thick.
  
  Kurt
  
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