Vintage Asylum

Cannot powder coat potted xformers... all the sand and tar would leak out from the heat*

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In Reply to: RE: How do you like this Factory built Citation 2? posted by Michael Samra on September 19, 2014 at 15:47:25

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RE: Cannot powder coat potted xformers... all the sand and tar would leak out from the heat* - Bold Eagle 11:16:22 09/22/14 (0)
Absolutely right. I used to work in the powder coating equipment business, and the oven temperatures are above 350 F for most coatings; but there are some spacial low bake powders for things like the oil filled struts that hold open car hoods and trunk lids. Those are coated after assembly with the oil and O rings already inside. I seriously doubt you could find the right color in a low bake. I'd stick with air dry liquid paint.

By the way, powder is generally not self priming, so you'd need to pre treat the parts before coating to get good adhesion.

Jerry
RE: Cannot powder coat potted xformers... all the sand and tar would leak out from the heat* - Brian Levy 08:07:42 09/21/14 (1)
So, would you not just remove the transformer and potting material, powder coat the outer side of the case and repot the guts? A bit of a mess but always wondered if there has been any advancement in potting that might be beneficial such as heat transfer.
Don Brian Levy, J.D.
Toronto ON Canada
- RE: Cannot powder coat potted xformers... all the sand and tar would leak out from the heat* - unclestu 12:37:00 09/21/14 (0)
  Many rewinders in Hong Kong do that: pop the bottom of the can off and use heat lamps to melt the potting compound into a catch pan so that they can reuse most of the original potting material, which may contain PCB's.
  
  I've seen the prints for a w-6 transformer and they potted the transformer with tightly packed crushed granite sand and then poured in the tar..
  
  IIRC the potting does several things. One is that it damps the transformer core to keep it from potentially buzzing. Second would be slightly better heat transfer with the use of the tar. The potting case would also act a partial shield.
  
  Companies like Algo Hamilton, at one time, offered transformer cases in aluminum, steel or mu metal for shielding. When I inquired two decades ago, the prices were a bit too steep unless I ordered in a large quantity.
  
  You could powder coat with out fear of leakage if you build a jig to hold the transformer upside down. IIRC powder coating runs temperatures about 400 F
RE: Cannot powder coat potted xformers... all the sand and tar would leak out from the heat* - Eli Duttman 12:11:51 09/20/14 (2)
Yes, the potting compound has a tar base, but the filler is ground slate. Nit pick aside, you are absolutely correct about not subjecting the "iron" to serious heat.

A "balls to the wall" refurb requires stripping the magnetics and repainting. A good self etching primer is the foundation on which a superior job is laid.

Eli D.
- RE: Cannot powder coat potted xformers... all the sand and tar would leak out from the heat* - rosendds@frontiernet.net 13:30:25 09/20/14 (1)
  If it were mine I would want to retain the original paint.The unseen modifications that Mike will do will make that amp sing with the best of them.
  - RE: Cannot powder coat potted xformers... all the sand and tar would leak out from the heat* - Michael Samra 13:37:05 09/20/14 (0)
    Thanks David.
    
    Honest amplification is better than excessive 2nd order distortion anytime.

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