[Collins] 872a Lamp, revisited

[David Knepper]

I would hope that this information on the lamp project is carried out with
safety in mind.

Dave, W3ST
Secretary to the Collins Radio Association
Publisher of the Collins Journal
www.collinsra.com
----- Original Message -----
From: Jim Brannigan <jbrannig@optonline.net>
To: Zap (Chris) <zap@xzapx.com>; <collins@mailman.qth.net>
Sent: Wednesday, August 27, 2003 4:32 PM
Subject: Re: [Collins] 872a Lamp, revisited


> The "glow" of a mercury vapor rectifier tube is proportional to the
current
> draw.
>
> Your power requirements are going to be considerable just to create a blue
> lamp.  For starters you will need a 38Watt filament transformer, they
don't
> come in miniature sizes.
>
> To "light up" the tube a HV supply of at least 2000V @ 500 mills is
needed.
> So you will need a transformer of at least 1000Watts and a resistive bank
or
> other current sink of at least 1000Watts.  These are large heavy
components
> and at that power level your "dimmer" would have to be a variac.
>
> Lastly, for safety sake the entire device should be enclosed in a metal
> chassis and have a good earth ground attached.
>
> Jim
>
>
>
> > Finally I need to finalize the circuit used to actually power the tube.
> > Unfortunately, I haven't been taught much about transformer theory in
> > school.  I'd like to find a specific (and smaller) filament transformer
> that
> > can fit in the enclosure.  Is this feasable?  Secondly, I'm also not
that
> > familiar with tube theory either.. so I'm not sure what to do with the
> plate
> > side, but I'm guessing that is where I will want to put the adjustment
to
> > dim/brighten the lamp.  Finally, I have no idea where to find the parts
> that
> > would be optimal for this project.  Here's the data I have so far on the
> > tube:
> >
> > Filament:
> > Average 5 Volts AC
> > Current @ 5 V avg 7.5A
> > Peak Tube Voltage Drop approx 10V
> >
> > Peak inverse anode voltage 5000 volts max (or 10000)
> > Anode current peak: 5A max
> > Anode current avg: 1.5A max
> >
> > Thanks in advance for any help you can provide.  This has been a
> back-burner
> > project of mine for too long, and I'd really like to see it become a
> reality
> > :)
> >
> > 73,
> > Chris, N9WIV
>
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