[Amps] Crowbar components

[Frank Goenninger]

Hi Rich!

On Thu, 2004-07-22 at 11:40, R.Measures wrote:
> On Jul 21, 2004, at 8:47 AM, Frank Goenninger wrote:
> 
> > Hi all on the list:
> >
> > There have now been several posts here pointing
> > to
> >
> > http://www.qsl.net/oe5jfl/flashover.htm
> >
> > as a suitable crowbar circuit. I want to copy that
> > one...
> >
> > When searching for suitable components I could not
> > find a suitable opto-coupled Diac as shown in the
> > mains circuit.
> >
> > My HV transformer will draw abt. 21A of current so
> > I need a Diac able to withstand that or I have to
> > substitute that part with ??? A diac controlling
> > a thyristor ? Or ??
> >
> > Are there any such diacs or what would a suitable
> > replacement circuit not altering speed too much
> > look like?
> 
> Frank --  Why go to the trouble of interrupting the flow of electric 
> mains current by special means?  The stored charge in the filter-C is 
> what can produce enough peak current to cause bent filaments in 3-500Zs 
> or gold to sputter from the grid of 8877s, and this current is already 
> limited by the glitch resistor -- provided it is able to withstand the 
> Joules available from the filter-C without going kaput.
> >

Well, I see the crowbar as a very elegant solution - and I've never done
one myself so far. So, technically speaking - I can't really say what
the killer argument for a crowbar would be. I see it as a second
protection in case the Glitch-R doesn't do his job or something else
happens out of the blue...

And, of course, building one and testing it is in itself a new one for
me.

73, Frank, DG1SBG