Review of BTC-3 Tesla Coil Kit From Information Unlimited
April 23, 1992
Eric Bush
Falls Church, VA
INTRODUCTION
Like many of you I am sure, I have read several autobiographies
of Tesla
over the years and have become fascinated with both the man and
his
inventions. I had for some time desired to actually BUILD a Tesla
coil.
Unfortunately, I suffer from a very poor education when it comes
to basic
electronics. The thought of building a device with such high
voltage
output was very intimidating to say the least! To my rescue came
the
Summer 1992 catalog from Information Unlimited. Add to this that
I had
quit my job (i.e. I had some time on my hands) and that $240
didn't seem
to be an unreasonable amount of money to spend for a time killer
(when
not searching for a new job) and dream fulfillment.
It occurred to me that there may be other Tesla novices out
there who
might be interested in trying to "feel the power" of
a real Tesla coil
fashioned with their own hands. This brief write-up will let
a novice
Tesla coil builder, whom chooses to start their Tesla building
career with
a BTC-3 kit from Information Unlimited, to have a better idea
of what to
expect if using the BTC-3 kit.
SUMMARY
The BTC-3 kit, when finally put together, delivered the 12"
sparks as
promised from the 250 KV output. However, a few screws necessary
for
the construction of the coil were missing from the kit and necessitated
a
trip to the local hardware store. The directions were cryptic
and the
drawings didn't match the eventual configuration as built. Some
parts
appear to have been substituted for those that were described
in the
directions requiring some improvisation in order to get things
to work.
The kit required very little in the way of tools, or knowledge
of
electronics, to put together and required a total of about 10
hours over
two weekends to construct. In spite of some of the changes required
during construction, I found the kit satisfactory and worth the
price.
I also went on to buy the optional Toroid Terminal after completing
the
coil and I would highly recommend it to anyone considering building
the
BTC-3 kit. While the bare wire coming off the top of the coil
produced
considerable sparks, it was only when I attached the Toroid to
the
secondary coil that the coil seemed to "come alive"
and produce an
incredible discharge field and a constant output of 10"
to 14" sparks.
Well worth the extra $69.
Now, I am ready to move on to building a 1 million volt coil
that I hope
to build from scratch! (with plans yet to be determined....)
DETAILED REVIEW
PARTS
An initial quick inventory of the parts in the kit as compared
to the
parts list included with the kit showed that several screws were
missing.
These are the kinds of missing parts that are very frustrating.
I
figured the long distance phone call requesting Information Unlimited
to
send me the screws would be more expensive than just going out
and
buying the screws. Other than that, everything appeared to have
been
included. I feel that potential purchasers of the kit should
also be
aware of the following:
- The secondary coil included in the kit was wound sloppily
and required
about two hours of my time to get it wound tight and without
any
overlapping wires. I began wondering if I couldn't have wound
a coil
from scratch in the same amount of time and saved the money of
having
to buy a pre-wound coil.
- There were no screws included with the kit that could be
used to
attach the top (the part that the secondary and primary coils
rest on) to
the tank enclosure containing the transformer, capacitor, etc.
- There were no screws included that could be used to attach
the
transformer to the bottom of the tank enclosure.
- The ON/OFF toggle switch included with kit did not match
the switch
in the plans and because of a protruding tab could not be attached
to
the side of the tank enclosure. I was forced to cut off and file
down the
tab.
PLANS & DIAGRAMS:
The plans include a nice brief introduction on Tesla coils
- what they
are and are supposed to do. The plans also include a nice conclusion
that describe options that the builder can add to the coil (that
will
produce additional effects and features for the builder).
The drawings and diagrams in the plans appear to be taken
from several
different sources, or at least drawn at different times by different
people. The formats of the drawings change frequently; in a couple
of
places two drawings of the same assembly on separate pages didn't
even
match. The drawings at times do not reflect the associated instructions.
This led to occasional head scratching moments of pondering on
how to
resolve the problem, "Do I go by the instructions or do
I go by the
drawings?!" Generally speaking, the drawings were accurate
and I used
them frequently to make sure I was on the right track.
INSTRUCTIONS:
The instructions were actually pretty good. Descriptions were
clear and
followed a logical stepwise path through the construction of
the kit.
Thoughtful comments are sprinkled throughout the instructions
indicating
pitfalls to avoid and/or variations that are possible as the
kit is put
together. One gets the feeling that someone had written the instructions
and then had actually gone through them and tested them for accuracy.
The only exception to my praise of the instructions, though,
is that the
instructions had not been modified to reflect obvious last minute
parts
changes that were shipped with the kit. There were also a couple
of
instances where the instructions were verbally correct, but the
drawing
referenced by the instructions appeared inaccurate and did not
reflect
the associated instructions. I'm not sure that this is a fault
of the
instructions or of the drawings?!
OVERALL DESIGN:
- An interesting conclusion drawn after the construction of
the coil was
complete, was that the kit required no soldering at all. For
peace of
mind (and for habits sake) I still soldered all the obvious connections,
but in fact didn't really need too.
- A finer treaded screw should be used for the spark gap adjuster.
It
takes quite a bit of fiddling to get the gap to the width that
provides
for continuous operation at maximum output.
- Generally speaking, the initial output of the coil was much
less than
advertised; perhaps 8" sparks at best. I added a second
capacitor
(identical to the one included with the kit) and wired it in
parallel with
the first and then got the spark output I desired. While it is
possible
that I didn't get the coil tuned properly initially, or that
I hadn't
assembled something properly, the addition of the second capacitor
did
the trick for output.
- The secondary coil comes with a plastic cap covering the
top of the
PVC tube used for the coil. This appears to be unnecessary and
in the
end I had to remove it so that I could patch some arcing that
was
occurring inside the tube.
- The plexiglass plate used in conjunction with the spark
gap adjuster
should have had an adhesive included in the kit for attaching
to the side
of the enclosure. I had to run out and buy some epoxy glue. It
would
have been a nice touch to have had this included.
- The power cord is supposed to be securely attached to the
tank
enclosure by using a plastic grommet. Unfortunately, the hole
cut for
power cord grommet was much too small for enclosed grommet.
- The neon bulb holder was too large to securely hold the
bulb. This
necessitated the elimination of the use of the bulb as part of
the
finished kit. This didn't effect the ability of the coil to run,
but it
probably would have added some "polish" to the look
of the coil when
completed and operational.
- It is an absolute necessity to corona dope all exposed wire
attachments
in the tank enclosure. Failing to do so leads to arcing inside
the tank
enclosure.
- I recommend that the secondary coil be insulated with a
coating of
paraffin wax as opposed to corona dope. The coil arcs through
a single
coating of dope as if it weren't even there. However, all arcing
was
eliminated with a single thin coat of paraffin wax. Its a heck
of a lot
cheaper than dope as well!
THANKS(credits):
A great deal of "thanks" goes to my good friend
Dr. Rin Saunders whom
without I never would have known about Tesla and whom acted as
a
patient guide and friend during the construction of the coil.
It was he,
back in 1986, that first enlightened me about Tesla. He had also
once
built a Tesla coil some 25 years ago as a young teenager and
was
therefore able to provide valuable guidance when the instructions
and the
diagrams (or parts) didn't quite match. I have included his commentary
on the kit and its construction above.