[Collins] 872a Lamp, revisited

[Jim Brannigan]

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