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Please Help
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From: Pete [SMTP:casius-at-cyberserv.co.za]
Sent: Tuesday, August 18, 1998 4:04 PM
To: tesla-at-pupman-dot-com
Subject: Please Help
Hi John Freau and all,
John, thanks for the welcome back. Was away from home and rather busy at
work with a project. It's nice to be back on the list. Thanks also for
your comments re my NST coil. I think I have asked most of the questions
before but I seem to have great success with valves and get wimpy sparks
with NST units.
Let me start from scratch. My NST Tesla coil is as follows:-
Two 12kv 30ma NST's in parrallel (total 60ma). The spark gap is directly
accross the NST (8 x 1/2 x1" Cu tubes spaced 0.015"). A bank of
capacitors in series (0.1uF x 8 = 0,0125UF at 50kV) comes off one side
of the spark gap and ties to the primary inside turn. The primary is a
12 turn 30 degree inverted saucer wound with 1/4" copper tube spaced
1/4". The coil is tapped at turn 7 and returns to the other side of the
spark gap. A 4" x 19" secondary wound with 22 gauge copper wire sits in
the centre of the primary. I calulate the frequency with toroid as
+/-348kHz. The spacing between primary and secondary is 1". The bottom
winding of the secondary is level with the 1st turn of the primary. The
bottom of the secondary goes to an out side earth via a 1/4" copper
stranded wire. The earth rod is 4 foot into the ground. The secondary
has a 9" x 1.5" toroid made of ribbed PVC pipe and wrapped aluminium
foil. A thin aluminium "plate" ( one of those disposable plates) sits
neatly on top of the wrapped PVC tube to complete the toroid which I
calulate at +/-10 pF. The toroid is 2" above the last winding of the
secondary. There is no NST protection.
Thats the setup. Even if I start tapping at turn 5 and go upto turn 8,
the best spark is 12". What could be the problem?. By the way the
capacitors are Plessy canned caps filled with visconol. There physical
size is 3"x2.5"x1.75" for each cap.I get the feeling that the problem
may be the caps I use.!!!!
Richard Craven,
If you are still out there. How's that 5CX1500A tube coil of yours
performing. I have had great results with my 5762 unit. The only problem
is that I have run out out power for the beast. Just can't supply enough
current. Had to settle for 650mm discharges for the moment. The 2 x 833A
unit is less hungry for power and is more manageable.
Regards
Pete Scully
South Africa