[Amps] Switching PS for filaments?

[F5HRY]

Hello,

Don't know if this has been discussed here, but basically a cold filament
has a zero Ohm resistance when you begin to heat it.

And as far as I remember, a switching PS does not really like to see a short
circuit, but I have never tested it mysef ...

BTW, I would favor a good old transformer.

73
Herve F5HRY

----- Original Message -----
From: "Tom W8JI" <w8ji at w8ji.com>
To: <TexasRF at aol.com>; <g3rzp at g3rzp.wanadoo.co.uk>; <amps at contesting.com>
Sent: Sunday, February 18, 2007 6:48 PM
Subject: Re: [Amps] Switching PS for filaments?


> > It may be 1 in 1000 but if you are the 1 you might well
> > think the number is
> > 1 in 1. After loosing the filament in a couple of 8877s
> > and a TH347 over the
> > years, I have become one of the fanatics!
>
>
> .....and you know the filament would NOT have failed anyway
> in that 1-in-1000 case WITH protection in that same tube
> because ......????
>
> Sometimes, like it or not, things just fail because they
> have a manufacturing defect. That sometimes triggers us into
> finding a pathological cure.
>
> That's certainly OK so long as we know we are leaping to
> conclusions. :-)
>
> Of course it is a good idea to not use a transformer and
> wiring that can dump 100 amperes into a 10 amp filament, the
> question is what really caused the failure.
>
> 73 Tom
>
>
>
>
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