1st light on small MOT coil

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

Original poster: "Wells Campbell by way of Terry Fritz <twftesla-at-qwest-dot-net>" <wellscampbell-at-onebox-dot-com>

hello, 

in a recent fit of activity, I cobbled together my scrounged MO parts
into a power supply, turned a cooler full of beer bottles into a cap
and fired a small coil. 

The power supply is two small MOT's and a level shifter arrangement where
the caps are in series with the HV transformer windings, diodes across
the other side of the caps to ground, and diodes out each leg to the
DC terminals. I believe the original to have come from Marco Denicolai,
and websites and info from Gregory Hunter, Steve Young, and Richie Burnett
were most helpful. 

I set up the power supply to be reconfigurable to Greg's other proposed
schematic (I believe it is a full wave doubler/filter?) simply by changing
a few jumpers. I'll send pics soon. 

Anyway, the PS in level shifter arrangement has four caps in series on
each leg, which limits current nicely. The output looks alot like a medium
neon transformer. Changing jumpers on the cap groups will increase current,
keeping voltage in the same range. I could use several different arrangements
to go from four caps per leg in series (.25 uF) to four in parallel (4
uF) (though this would probably be too powerful). I ran low voltage tests
to confirm the nature of the output (cheep DMM) then ran it through a
copper cylinder type static spark gap (no cap) and got the familiar purple
sparks, buzzing along at a clearly audible 60Hz. 

I couldn't wait on the caps to come at that point, so I took about an
hour to cobble up a small saltwater cap with beer bottles and a cooler.
14 bottles in all. my meter says this is about .003 uF, which if I remembered
from my coiling in the past, would get me ballpark for a small coil.


I then used an extra coil (3.5" by  16", 27 AWG ~ 1100 turns) and magnifier
primary (14" dia. cylinder shape) in a normal coil arrangement (my maggie
secondary has no wire yet) and brought up the juice. the gap sparks had
that familiar snap now with the cap, and-- the end wire of the secondary
had a small purple fuzz to it! I retuned to about four turns, and the
whole top of the secondary was haloed with purple, spiky little sparks
about 3" into air. I quickly added topload, (alum. pot lid) retuned for
about five turns, and got 4" spikes. A ground wire produced 6-7" point
to point arcs which were a little brighter, and popped along with the
60 hz. buzz from the gap. Increased power actually reduced performance
somewhat, as the cap would arc multiple times during the duty cycle and
fire chaotically. Anyway. I'm quite pleased at having the ability to
throttle down the power with no mains current limiting, and the general
adjustability the design affords. 

I also hooked up a MOT and de-Qing diode, to see if the charging choke
effect would work. I measured only about a 10 % rise in voltage in low
power mode, and the output of the coil seemed to be about the same. I
think that the pulses of the level shifter with no filter cap to supply
a constant voltage is to blame, also no rotary gap. I will investigate
this later, after I have built the maggie, and a rotary gap (gripe) 

Now I need to wind the magnifier secondary, add protection and bleeder
resistors (some caps must be discharged by hand) and get a nice big tank
cap. 

Thanks to those who supplied info, it was most useful. I'll keep updating
and hopefully have some pics...

Anyway, the ozone smelled pretty fresh, after more than 3 years...

-- 
Wells Campbell
wellscampbell-at-onebox-dot-com - email
(415) 430-2169 x3756 - voicemail/fax



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