Re: It Just Stopped

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

Original poster: "Gregory Hunter" <ghunter31014-at-yahoo-dot-com> 

Sounds like a shorted cap or a shorted NST secondary.
Try running it without the cap and see if it can fire
the spark gap. If it gives an orange, flaming arc,
it's a shorted cap. If it won't fire the spark gap, or
if the arc is very weak and spindly, you have a
shorted NST secondary.

BTW, the cap may read good on a cap meter, but still
have a punctured layer that only arcs thru at high
voltage. This is especially true of oil filled caps
where the flowing oil "self-heals" just good enough to
fool a cap meter, but not good enough to prevent HV
arcing at the site of failure.

Cheers,

--- Tesla list <tesla-at-pupman-dot-com> wrote:

 > Original poster: Mddeming-at-aol-dot-com
 >
 > Hi All,
 >      Something happened last night that has me
 > puzzled. I was testing 4.25"
 > coil. It had been run intermittently for about 1/2
 > hour. I fastened a
 > pointed rod to the center bolt of the topload (dual
 > toroids) pointing
 > upward, preparatory to making a "pinwheel". I was
 > getting nice 3ft+ arcs to
 > the ceiling of the lab, (coil is caged 10' x 9' x
 > 8'.) After about a
 > minute, it suddenly went dead. No arcs, no gap
 > spark, no sound except the
 > vacuum on the sucker gap. It had been drawing ~18
 > Amps on 30 Amp circuit
 > prior to problem. Indicator lights showed power
 > reaching primaries of NSTs.
 > Variac output showed 120V. No racing sparks noted,
 > no arcing to primary. I
 > shut system down, waited ten minutes, tried to
 > restart... Nada!
 >      I disassembled everything and checked each
 > component:
 >
 > Xfmr 1 Allanson 15/60:  6000v left and 5990v right
 > to ground terminal with
 > 102V input. (My HV meter limit is 6 kV)
 > Xfmr 2 Transco 15/60: 5995v left and 5980v right to
 > ground terminal with
 > 101.8v input.
 > Tank cap: Maxwell 37xxx series, 30 nF nominal,.
 > measured 29.95nF with RdShk
 > DMM and 30.91 on AADE L/C II-B. On the 14th of July,
 > it measured 31.07nF on
 > the L/C II-B when air Temp was 11F warmer and
 > Humidity was 30% higher.
 > Sucker Gap 1 HP vacuum spaced 7.5 mm.
 > Safety Gap spaced 5 mm Left and 4 mm Right.
 >
 >      Reassembled everything and... Nada!!
 >
 > Any Guesses??
 >
 > Matt D.
 >
 >
 >


=====
Gregory R. Hunter

http://hot-streamer-dot-com/greg