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PC board Capacitors

Quoting rickh-at-ghgcorp-dot-com (Rick Holland):

> ... I wanted to share my discovery that double sided PC board
 > blanks seem to make decent capacitors. I etch a 3/4 inch border
 > on them and solder the leads on. I've used these on a 7.5kv
 > neon with no breakdown. Of course, I have no idea what their
 > efficiency is, but I imagine Mr. Quick has stumbled across this
 > before and may have some data for us (I hope I'm not presuming
 > upon Mr. Quick).

I looked into this methode 2 weeks ago. General Electric rates their FR4
fiberglass epoxy circuit board at 75KV for 0.062", E is 4.7 and I forget
what the disapation  factor is (it's at work). But I calculated that I
needed a square meter of it to get the capacitance I wanted, and did not
want that much exposed HV just lying arround.

Richard Quick said:

>The last word in homemade capacitors are plastic film dielectrics
 >submerged in mineral oil. They rate right up next to commercial
 >plastic film pulse discharge caps.

And I believe him NOW. I just finished blowing 2 caps in my TC primary last
night. I'd found some surplus 0.015uF 6.5KV DC film caps for $.99 each. I
bought 10, wired 9 in series/parallel to get 0.015uF at 19.5KV. I was
running about 6KV into the primary of my TC so I figured that a 3:1  safety
margin was ok. WRONG! Both times that I approached resonance, beautifull
little sparks started showing thru the case of the caps:( Every time I try
something new of my own design I prove to myself Richard's hard won wisdom.

I'm still argueing with myself over wether to build a oil and film cap or to
order one from Condenser Products.

I can tell you though, don't was your time with doorknob caps and 14 gage
primaries! 4" sparks vs. 12" with dc rated caps and 1/4 copper tubeing
primary. I can't wait to see what length sparks I'll get with a real pulse
rated cap.

                        jim



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