[Amps] Switching Supplies for High Current Filaments

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Tue, 5 Oct 2010 07:34:41 -0700, Patrick Barthelow
<apolloeme at live.com> wrote:

>Would cold start surge current be a problem for switcher implementation for filaments

REPLY:

Surge current would be a problem if the supply is regulated, which most
of them are. Just put a suitable resistor in the filament lead with a
relay to short it out after a few seconds delay. 3-500Zs have a
reputation for being damaged when run without surge protection.

Another problem is using DC on a filament-type tube such as the 3-500Z.
(I assume you are talking about using a DC switching supply).  This
places a bias across the filament - the side of the filament with the
negative supply will emit more than the other. I don't know how much of
a problem this is, but it doesn't sound good. Perhaps someone else here
has more definitive information.

73, Bill W6WRT