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Re: High Voltage Potting



Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

> Hi Ed,
> This is strange because i found that a double boiler would melt the glue
> sticks in the wax very nicely? maybe it depends on the "hardness" of the
> sticks, not sure?
>  And to be perfectly honest, I think the straight polyethylene strips
> made a much better potting mix, It just requires much more patients to
> smooth out.
>  I found that a small "wisp" moved in a very slow figure 8 pattern
> worked best for smoothing the poly\wax mix without air introduced. I
> also found that when trying to fill complex shapes or a block that has
> many free items in it, It works best if melted straight wax is poured in
> and on the (diodes or whatever) then rolled around to give a thin coat
> over everything. Then when the poly\wax mix is poured in, It seems to
> displace the straight wax giving a total coverage without air pockets.
> 
> You are correct that there is some shrinkage, I was mistaken by saying
> that there was "none", But i usually "TOP" off the mold while the mix is
> hot yet solid. This bonds together as a one pour unit.
>  Thanks for the correction because it has been a while and my memory
> needed a jolt to get the facts.
>  Either way, this (80% poly\20%wax) mix is the best potting mix i have
> tried.
> Now there are high voltage potting mixes on the market that claim higher
> yields then this mix. I have seen adds of silicone or epoxy mixes in my
> tech. magazines that sound very promising, but i have yet to try any.
> Take care all,
> Marc M.

	Thanks for the note.  I never thought of using a double-boiler (not
sure my wife has one any more or that she's ever let me use it in the
kitchen).  When I did the things I mentioned I was using a hot plate
with exposed wires, not exactly the safest thing in the world.  I did
have a thermometer in the paraffin, and found that I had to run the
temperature up around 260 F to get the polyethylene strips to melt and
dissolve, so we may be talking about different material.  I don't know
what the differences between the different glue stick melts are, but
presume one would want to use the lowest melting temperature available. 
Would that be the slowest setting?

	I'm still very much interested in this topic, as I want to pot a pair
of GMHEI coils in a nice oak box, to simulate an old-fashioned
"induction coil", and don't want to think of messing with oil.  Someone
suggested using vaseline, but I'm afraid even that would eventually
destroy the finish on the inside of the box and soak into the wood.

Ed