Super Thumpy Update 11-1-99

     The Auto Thumpy is a magnetic pulser described on keelynet. 
It uses the large party strobe from Radio Shack. After building
one of those, I found that there was a resistor in series with
the strobe that would get hot because of the larger capacitor
that I had added.  So I went out and bought the small party
strobe from Radio Shack,  part number 42-3048.  I turned off and
unplugged the unit, and then took out the 4 screws that hold the
cover on, the 4 screws that hold the printed circuit board down,
and the 2 screws that hold the strobe cover on.  The strobe
housing and chassis slip right out without disconnecting any
wires.  (Please do not try any of this if you do not know how to
identify a capacitor or discharge it.  You could be injured or
worse.  These strobe units are very dangerous even when not
plugged in due to the charge in the capacitor.)  I made sure the
capacitor was discharged, and cut the wire leading to one end of
the flash tube, leaving enough length on each end to attach the 4
feet of 16 gauge speaker wire that goes to the coil.  The coil is
MCM part number 50-940.  It is important to cut a wire leading to
an end, not the middle of the flash tube.  The coil wire exits
the box through a hole in the upper right corner of the front,
just above the power cord hole.  A grommet protects the cord. 
After attaching the coil and making sure that nothing was shorted
out, I plugged in the still disassembled unit and turned it on. 
The pulse was rather feeble as expected.
     The large capacitor is a 9uf at 600 volts.  I measured the
voltage on the capacitor.  It was just over 250.  The contact
near the center of the printed circuit board is the negative end. 
I wanted a 200 or so uf at 600 volts, but was unable to find one
at Supertronix.  So I settled on a 100uf at 450 volts.
     With the device unplugged and the capacitor discharged, I
removed the capacitor and replaced it with the new one.  All
connections were insulated, and the coil wrapped with electrical
tape, as this is an experimental magnetic pulser, not a shock
therapy device.  I also put black electrical tape over the clear
flash tube cover.  With credit cards and other magnetic material
removed from the area, I tried out the modified device.  Very
nice pulse.  Looks  better than the Radio Shack strobe in the
larger box.  The circuit board also looks much more robust and
the capacitor fires the strobe directly, so there is no series
resistor overheating in this one.  Much better device.
     More recently, I discovered that All Electronics has a 300uf
at 320 volts that is physically small.  So last night I put one
of those in a Super Thumpy using wires that are about 3" long. 
Worked fine.  There was plenty of room for a second one, so I
added it.  Very powerful pulse, but it takes about two seconds to
charge.  I am not sure if the tube and related parts will put up
with this much power for long, so I am using one at home on a
trial basis to see if it breaks.

     Bob Haining has designed a much more powerful pulser which I
hope to be able to experiment with soon.