[Amps] tube fils..again

[Dave White]

I've known plenty of people use ex-computer 5V DC switch mode supplies for the heaters on oxide cathode tubes like 4CX250Bs (G6ABU used them for years in his 2 metre contest amps) - probably because they're stable, cheaply available and easy to set-and-forget.

I've not heard of anyone using DC with tungsten filaments though.  It's a good question.

Dave DL/G0OIL

----- Original Message -----
From: Jerry Kaidor <jerry at tr2.com>
Sent: 16 June 2012 18:10
To: amps at contesting.com
Subject: Re: [Amps] tube fils..again

I was thinking about this last night.  AC is hard to regulate.  Has anybody
thought of running filaments off DC?  DC is easy to regulate.  Cheap
switching power supplies can deliver large amounts of efficiently
generated, tightly regulated DC.  Turn-on and turn off ramps can be
precisely controlled.

   Regulating AC OTOH is hard.  Techniques I can think of off the top of
my head include - special transformers with IIRC air gaps that are
controlled
with DC windings that partially saturate them - transformers with multiple
primaries or secondaries chosen by Triacs or SCR's - small motor-controlled
variacs - powerful AC amplifiers with gain feedback...

                        - Jerry Kaidor, KF6VB





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