Re: SSTC probs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jan Florian Wagner by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jwagner-at-cc.hut.fi>

hi fucian,

4.5" x 12" with #28 should be around 300kHz I think... well you can also
use freeware tesla coil design progs like wintesla and others:

  http://www.g8cyerichmond.freeserve.co.uk/download.htm

> I got the IRF740 to take about 70 volts and then POOF!No smoke or 
> anything.Just failure.It looks perfectly fine.Replace it and im back in 
> buiseness.It doesnt even get hot when it fails.WHY?

Believe me - it's because of overvoltage! That's why it does not explode
or get hot.

Try a 250VAC varistor/MOV/VDR accross the mosfet, and leave out all those
diodes around the mosfet! Also, place a 18V Zener between gate and source,
the "wrong" way round i.e. pointing towards the gate.

> The 555 pulse circuit is using a 102K capacitor(.001uF right?) for timing
and 
> 2 1k resistors in series with 2 10k pots.Shouldnt this be good for up to 
> 480khtz?

Yup, thats 100% fine! :o)
 
> So, total results from my little 555+IRF740 MOSFET setup is 1inch orange
fire 
> arcs.Is this good for a simple 555 setup?Or am i missing something?

It is nice. Of course, there's always room for improvement ;o), you could
be expecting something like ~4" or longer, real streamers, at ~100W.

Try out a number of different primary turns until you get max output. The
primary should not be flat but helical, and wound along the lower part of
the secondary.
 
 - Jan

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