From: mac@cis.ksu.edu (Myron A. Calhoun)
Newsgroups: rec.radio.amateur.misc
Subject: Here is a TV flyback Tesla design
Date: 27 Sep 1992 01:47:24 GMT
Organization: Kansas State University, Dept. of Computer Science
Distribution: na
NNTP-Posting-Host: depot.cis.ksu.edu

While cleaning up my workroom I found a schematic for a "TESLA COIL KIT"
sold (many years ago) by B & F Enterprises, 119 Foster Street, Peabody,
Massachusetts 01960 (617) 531-5774:
                                         O CAP terminal (VERY HIGH VOLTAGE!)
   +--------------------------------+    |
   |           +------------+       |    |
   |        | /             |       |    |
   |        |/              |       | || $         ******** DANGER *******
   +--------|               |  L2 = $ || $         *                     *
     2N3055 |\       L1 = 4 $   10  $ || $ L3      * I TAKE ABSOLUTELY   *
            | v       turns $  turns$ || $ is a    *                     *
              |             $       $ || $ fly-    *       ** NO **      *
              +---+      +--$    +--$ || $ back    *                     *
              |   |      |  $    |  $ || $ xfrmr   * RESPONSIBILITY FOR  *
            | ^   |      |  $    |  $ || $         * YOUR USE OR ABUSE   *
     2N3055 |/    |      |  $    |  $ || $         * OF THIS CIRCUIT!!!  *
   +--------|     |      |  |    |  $ || $         *                     *
   |        |\    |      |  |    |  | || $         ******** DANGER *******
   |        | \   |      |  |    |  |    |
   |           +--|------|--+    |  |    +------o 1  8  -  5  Pin connections
   +--------------|------|-------|--+    +-----o  8  7  5  4  to the following
                  |      |       |       +----o   5  6  6  2  flyback 
                  |      |       |       +---o    7  4  8  1  transformers:
                  |      |       |           |    |  |  |  +-- 738192
                  +------|-------|-----------|    |  |  +----- 32-10008-4
                  |27 ohm|240 ohm|           |    |  +-------- 32-10014-1
                  +--R1--+---R2--+           |    +----------- 32-8859
                  |              |         -----
                  |              |         /////
                  -   12 volts   +

Quoting from the instructions:

  "WE TAKE NO RESPONSIBILITY FOR YOUR ACTIONS!!!

   The new windings must be added to the flyback transformer to allow
   adequate transistor drive capability.  These windings are hand wound
   on the bottom leg of the ferrite core where the original filament
   winding was located.  Remove and discard the original filament winding.
   In its place, wind first a ten turn, center-tapped, winding using
   approximately 30 inches of #20 or larger hookup wire.  This is easily
   accomplished by winding five turns at one end of the core and then
   twisting a loop in the free end before adding the second five turns.
   The complete ten-turn winding should then be held in place with a turn
   or two of electrical tape with the two ends and the center loop all
   protruding.  Connection can be made to the center loop when the
   insulation has been carefully removed.  If it becomes necessary to cut
   the center loop, be sure that the two ends are scraped and joined to
   form a mechanical as well as an electrical center-tap to the winding.
   [L2 in my drawing]

  "The second winding should be wound directly on top of the first but
   it should only have a total of four turns--two each side of the
   center-tap.  Again, wind two turns of #20 or larger hookup wire, pull
   and twist a center loop, and wind the other two turns.  Tape this
   winding in place on top of the first.  Do not let the center taps of
   two windings touch each other but they should not be more than one
   quarter of an inch apart.  [L1 in my drawing]




  "Wire the modified transformer to the transistors and the bias circuit
   resistors as indicated on the schematic circuit diagram.  Be sure to
   mount the transistors on a suitable heat sink with the insulating
   hardware provided to protect them from over heating.  Since the
   collector connection of these transistors is made to the case, it is
   necessary to keep them electrically isolated from one another and
   from the heat sink and insulators are provided to allow this.  Heat
   sink area of approximately 25 square inches should be adequate.  If,
   however, the power transistors become too hot to hold a finger on,
   more heat sink area should be provided.  Heat sink material of one-
   eighth inch aluminum is desirable.

  "Note:  If Oscillation does not start Immediately Interchange the two
          Transistor Base connections [capitalization as in original!]

  "CAUTION:  LETHAL VOLTAGES ARE INHERENT IN THIS DEVICE.  EXTREME
   CAUTION MUST BE EXERCISED TO KEEP THE FULL OUTPUT OF THIS DEVICE
   FROM BEING APPLIED LIMB-TO-LIMB OF ANY LIVING ANIMAL.  SEVERE BURNS
   OR DEATH MAY RESULT FROM CONTACT WITH THE FULL OUTPUT..."

There were other instructions about how much damage might accrue to a
human if contact were made to the high-voltage output, so BE CAREFUL!

I used one-half watt resistors for R1 (27 ohms) and R2 (240 ohms) and
got a nice Jacob's ladder effect.  It also wiped out most of the
computer terminals in the entire building, so I couldn't run it very
much!  I later tried 18 volts and one resistor zapped immediately!
--Myron.
-- 
# We preserve our freedoms using four boxes:  soap, ballot, jury, and cartridge.
# Myron A. Calhoun, PhD EE; Assoc. Professor  (913) 539-4448 home
# INTERNET: mac@cis.ksu.edu (129.130.10.5)          532-6350 work, 532-7353 fax
#     UUCP: ...rutgers!depot!mac     Packet-BBS: W0PBV @ K0VAY.#NEKS.KS.USA.NAOM
Newsgroups: rec.radio.amateur.misc