Re: PC board cap is a no-go

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "rheidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

Shad: I'm sorry to hear of your trouble. I use both LDPE/flashing/oil
capacitors and PC board capacitors with good sucess.I use mill spec boards
heat striped 1 inch from the edge NOT etched.  I use 12 layer 4mill LDPE and
oil with 1 inch straps, 2 on each end of each cap of 4 parallel cap bundels.
This gives me 8 ea 1 inch straps on each end of my flashing caps to carry
the current. My PC board caps only delivers 400 amps each so I use 2 sets
parallel at 22KVDC ( NST 15/60 center grounded HV diode stack rectifiers)
2 double sided boards on - 11KVDC and 2 double sided boards on + 11KVDC.
   Robert  H    
> From: "Tesla list" <tesla-at-pupman-dot-com>
> Date: Thu, 25 Apr 2002 18:58:23 -0600
> To: tesla-at-pupman-dot-com
> Subject: PC board cap is a no-go
> Resent-From: tesla-at-pupman-dot-com
> Resent-Date: Thu, 25 Apr 2002 19:08:05 -0600
> 
> Original poster: "Sundog by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <sundog-at-timeship-dot-net>
> 
> Hi All,
> 
> I was looking at etching the copper from PC boards and using them as
> elements of a flat stacked cap for the GU10A tube coil.  I *finally* got
> the chance today to set up a test.  12kv NST,  fullwave rectifier, and a
> variac on the NST input.
> 
> It failed pretty miserably.  There was a lot of corona losses at the
> edges of the plates, even at ~11kvDC.  Puncture resistance was okay, but
> the sustained corona quickly weakened the dielectric enough for it to punch
> through after about 2 minutes of sitting at ~13kv DC (that'd be pretty hard
> on the GU10A).
> 
> Yes, I could stack 2 plates together in series to halve the voltage
> across each one, but that would immediately quadruple the space needed, and
> also the cost.  Where before I'd need about 30 plates, I'd now need
> 120.  At around $4 each, it's now real expen$ive.
> 
> So I need an alternate plan here guys.  I'm up the creek without a
> suitable cap.  MMC's are out of the question.   Too much capacitance, not
> enough current handling ability.  transmitting caps are hard to find and
> expensive, and I don't know of any home-made cap that will take the raw
> current (much higher sustained current than a TC can deliver).   I get the
> feeling LDPE and aluminum flashing caps would get too hot and disentegrate
> internally, leading to a spectacular and probably fatal (to the tube)
> failure.   I'm open to suggestions.
> 
> Thanks all!
> 
> Shad Henderson
> G3-1203
> 
> 
>