On Sun, 16 Oct 2005 18:29:24 -0400, Joseph Gwinn
wrote:

In article ,
Eric R Snow wrote:

On Sat, 15 Oct 2005 23:26:26 -0700, "william_b_noble"
wrote:

high voltage mica caps aren't hard to find, I have a 30,000 VAC mica cap
sitting here at this moment - it's about 8 inches X 6 inches X 12 inches,
with a 8 inch insulator on top, the case is one terminal, the other is on
top of the insulator.

I suspect your TIG welder needs a lower voltage.

Mica has particular dielectric benefits in certain frequency bands - and oil
dripping out is not a real problem, jsut remove the cap, refill with oil and
seal it again. use mineral oil if you can't find capacitor oil.


Capacitor oil kinda sounds like skyhooks and file grease. I'm sure
it's not. I'll look for it and try to see why the things are leaking.
Will oil loss make the capacitance lower?

No. The oil is to prevent flashover within the case, and to cool the
mica, which does the heavy lifting. Flashover within a capacitor in a
welder may destroy the capacitor, so I'd make sure there is enough oil
in the capacitor case.

Joe Gwinn
The oil has been leaking for a long time. I thought it was something
else. If flashover occurs will it act like a short? And would this
prevent any high frequency at all? I ask because the high frequency is
weak and always has been. But it is there. The spark gaps work. But
every Goldstar machine I've used has been the same. Maybe they all
have defective caps. On Lincoln machines you could see purple sparks
emanating from the tip of the tungsten and dissipating into the air.
But Miller Goldstar machines I've used never would do that.
Eric

Eric
" They are mica capacitors. Can types other than mica be
used? And can they be paralleled to increase the value? Is there a
better type than mica? And finally, does anybody here have some to
sell?
Thanks,
Eric R Snow