Neon Power Supplies

 * Original msg to: Rmr-at-christa.unh.edu
 * Carbons sent to: usa-tesla-at-usa-dot-net

Quoting Ryan Ruel <rmr-at-CHRISTA.UNH.EDU>:

> I have read the guide to getting neon power supplies for free. 
> I tried to call the local neon shops, (there's only two within
> an hour of me), and received response from only one of them.  I
> bought two 15 kv, 30 ma units from a repair man for $30 a 
> piece.  He has more, but I will have to pay for them.  

$20.00 - $25.00 apiece is a fair price for these if they are
used, tested good while you watch.

> My problem is that one of them has burned out. I unpotted it, 
> and it worked for a while.  I then ran my coil a bit, and one 
> of the windings burned (I mean FLAMES!).  It's now pretty much
> dead.  

I guess so!

OK, I need to expand on the operational difficulties and mention
some pointers for improving the neon's life span as a Tesla coil
power supply.

The neon transformer is not designed for this application. It is
being pressed into much rougher service than intended. The
pulsing of the HV line and RF oscillations really beat up on the
very fragile secondary windings. This is especially true of the
30 ma neons which are the most common. Here are some pointers:

First off is the shunting block. These little blocks positioned
in the core between the primary winding and each of the two
secondaries is the current limiter. If you want more power AND
long transformer life, leave the shunts alone and add another
transformer. If you break a core all the way down for a repair or
rebuild make sure you keep track of every plate and replace them.
One or two shunt laminations make all the difference to the
transformer life span. This is especially true on the more common
30 ma cores. They just won't tolerate much fiddling with the

Second, you MUST have a properly safety gap on the power supply.

Third, with neons I strongly advise that a small high voltage
bypass capacitance be placed across each high voltage line to
ground. The value of this bypass capacitance should be very
small; a few dozen picofarads is much better than nothing.

Forth, use a heavy ferrite toroid RF choke in series with the
line to the tank circuit. I am becomming convinced listening to
comments and conversations out here that the RF chokes are being
ignored. It seems that it is difficult to make these chokes have
too much inductance, and the tendency is to make them too light.
For the novices out there who are learning the ins and outs of
tuning, coupling, toroid loading etc., these chokes are really
going to add life to your neon power supply if you wind enough
inductance into them and use them.

It is better to add extra neons with the secondaries in parallel
than to force the full load of even a small coil on one or two
cores. By ganging up a few neons in parallel you distribute the
load among several cores. My experience has been that the life of
all of the neon transformers in the bank are extended, the coil
performance is also improved.

Richard Quick

... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12