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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 intimi-
dating to say the least!  To my rescue came the Summer 1992 cata-
log 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 satis-
factory 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 expen-
sive 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 instruct-
ions.  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.  
