WAY OT! Re: [SEL] Early Switchboard Meters and Switchgear

[John Culp]

Curt, I don't fool with that newfangled solid state stuff much at all. 
I wasn't the one who brought up snubber diodes, I pointed out that they 
were a silicon analog of a tube. If what I'm working on doesn't have 
tubes in it, I feel like a stranger in a strange land! RC circuits do 
work well for voltage spike protection on tube amp output circuits, as 
does a simple resistor across the secondary in the ratio of, say, 20/1 
to the load resistance. Spoils the Q of the transformer just enough to 
keep it from frying things if the speaker's left unconnected and a 
transient gets into the amp input. An RC series across the 
transformer's primary serves the dual purpose of also shaping the tone, 
filtering off highs. It's been called a "conjunctive filter." It's not 
quite a simple low pass filter, as it is in parallel with the 
inductance of the transformer primary, so there's an LC resonance also 
involved.

Yeah, 5Y3GTs are a good old rectifier tube! I've got a big old radio 
that uses that. Been in the family since 1951. Every once in a while I 
have to fix it. :-)

John

On Jul 18, 2005, at 2:17 PM, Curt wrote:

> John,
> Since you have changed from DC circuits to AC circuits,  I gotta ask, 
> why use a solid state device for energy absorption when a simple 
> rugged RC circuit does well?
> I've not seen these quenching/spike diodes you mention used anywhere 
> on contacts or coils. Are these simply zenors?
> On your tubes.....5Y3GT 's? I think I've still got a few of those.....
> Curt Holland
> Gastonia, NC


John Culp
Bristol, Tennessee, USA