On Wed, 12 May 1999 08:33:05 +0100 "Ian White, G3SEK"
<G3SEK@ifwtech.demon.co.uk> writes:
>
> Radiodan W7RF wrote:
> >
> >Do your thoughts on the negative lead or positive lead glitch
> resistor also
> >hold true for DC choke (choke input ps)?
> >+ or - OK, but with a greater need for insulation when placed in
> the
> >negative lead?
> >
>
> I believe so... a choke input supply still needs a glitch resistor,
> to
> handle the current surge out of the smoothing capacitor. If the
> choke
> and resistor are in the negative side, the choke would connect to
> the
> junction of the glitch resistor and the negative end of the
> capacitor.
> That point will spike towards several kV negative if there is a
> "crowbar" short from B+ to chassis, and if that point arcs to
> chassis
> the surge current will bypass the glitch resistor.
>
> Once again, it implies that the choke would need to be insulated to
> broadly the same standards as if it were in the B+ lead. The
> difference
> would be that in the positive lead the voltage stress to chassis is
> present all the time, while in the negative lead it only happens in
> rare
> emergencies.
>
> 73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
> 'In Practice' columnist for RadCom (RSGB)
> http://www.ifwtech.demon.co.uk/g3sek
Am I not suprised to hear that this is new news to Henry? Old sparkies
as Rich, Carl and others have mentioned.
Cheers Norm
.
>
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>
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