Re: 24 turns center tap neon primary.

Tesla List wrote:
> I also discovered that you can not build a DC to AC converter using SCR's.
> It won't work.  When the SCR is triggered it won't open again until the
> power it turned off.  After about 2 seconds every solder connection melted
> and the entire circuit fell apart into a pile of parts on the work bench.  I
> didn't know what happened the first time so I soldered it all back together
> and did it again.  Its a little funny, wish I had it on video tape, the
> circuit is soldered together one second, then all at once the entire thing
> falls apart all by itself. Look its magic.
> Gary Weaver

The usual strategy with SCR's is to build a CT primary, with an SCR in
each leg to return, and a capacitor between the two legs. (Say the CT is
positive, with the two ends connected to the anodes of the SCRS, the cap
would be between the anodes.) Assume 1 SCR is conducting.

     |                  |                       |
     |                  |        |  |           |
     |----------------- | -------|  |-----------|
     |                  |        |  |           |
     |                  |                       |
     |                  |                       |
    SCR 1             +Supply                 SCR 2
     |                                          |
     |                                          |
    - Supply                                -Supply

The cap will charge so that it's right end (the end connected to the
anode of SCR2) is positive (because the anode of SCR1 is low voltage (it
is on)).  Now, fire SCR2. This momentarily reverse biases SCR1 (because
the negative end of the cap is there, and the inductance of the
transformer keeps it from discharging too fast) turning it off.  The cap
charges up with the left end positive, etc....

Naturally, this requires careful selection of switching rates, the cap
value, and the transformer inductance. My GE X-ray power supply switches
at 500 Hz.