Re: SSTC probs >> RF burns, notes, 3055's, etc.

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Pyrotrons-at-aol-dot-com>

Hi All.

I've been following this thread, thought I would jump in and clear at least a 
couple things up.

First and foremost: I designed the circuit at www.hvguy-dot-com to drive TV 
flyback transformers with 5 to 15VDC input, not for SSTC's running some kind 
of ungodly high voltage input ; )) I just thought it was interesting that it 
would sorta kinda work with a high Q air-core resonant transformer! The 
circuit has no real protection for the MOSFET, that is why there are problems.

About the "I'm getting RF burns all over the place" issue ; ), I'll make a 
bold statement and say that there is no way to cure that. If you are close to 
the coil, and you touch something conductive, you will get burned. This is 
because nearby objects/humans are capacitively coupled to the HV output of 
the coil, and capacitors pass AC current >>> capacitors (human or non-human) 
will pass 300kHz HVRF like a wire will pass DC......so anyhow I don't think 
this is a grounding issue. Even the small pF offered between a human and a 
SSTC is enough to hurt ; (

The half-bridge and full-bridge circuits are fantastic. If you're going to 
get into SSTC stuff, go with those. I highly recommend the schem's on Richie 
Burnett's site, at www.richieburnett.co.uk. I would modify his stuff only a 
couple of ways, and that is to simply add MOV's across all the MOSFET's from 
drain to source. MOV's are very fast devices and work well for this HV 
transient suppression stuff.

I layed out Richie's H-bridge board tonight, I hope to stuff it tomorrow and 
test it sometime this week. I'm using 4 IRFP460's (500V 28A) that Aron gave 
me. For the protection diodes I'm using 5822's and SF56's......they are 400V 
50nS jobs I think, they should work well.

Also got the primary and secondary finished, the pri is 12 gauge THHN on 6" 
PVC, the sec. is 4" x 16" with 28.......a nice pretty orange....

BTW the TL494 based stuff on Richie's site works well using good 'ol 2N3055's 
and TIP42's for the drive transistors.............he is using ZTX450's and 
ZTX550's as I'm sure that's either what he had, or what he could easily get 
in the UK. I'm hoping to "Americanize" Richie's H-bridge design, I've got a 
nice list going of some tried-and-true replacement parts.

Have to run, wish me luck with the $25 of P460's this week...........!! 
Hopefully if one goes it won't take the others with it. Of course, I will let 
you all know how it goes.

Take care,

Justin Hays
KC5PNP
Email: pyrotrons-at-aol-dot-com
Website: www.hvguy-dot-com