SWTPC Digi-Vista Nixie Clock

[Tony Duell]

> 
> woodelf wrote:
> > I would have updated the high voltage power supply to a simple
> > transistor regulator. I have about 128 AC around here and that
> > can really give  over voltage on 115 V transformers.
> > PS. Where do you find a 300 V transformer ... I may build one
> > some day.
> 
> If you don't want to scrounge surplus stores, or wind your own, Hammond
> currently makes a couple that would work.  They are the 269BX and
> 369BX, depending on whether you want "universal" primaries or not.
> Their high voltage secondaries are 300VCT, and they also have the 6.3V
> windings.  They're a bit larger than necessary, being rated for 2-3
> times the power called for in that design.

If this is just to power the nixie tubes, then the current required is 
pretty low. You would probably manage it with a mains transformer used 
backwards, running off the logic supply transeformer : 

Suppose the logic supply transformer has a 9V secondary. Get another, 
smaller power, mains-to-9V transformer (say use 50VA for the first one, 
20VA for the second, those are likely to be overkill). Connect the 
'secondary') of the second, smaller, transformer to the secondary of the 
first one (which still supplies the logic PSU circuit). That second 
transformer will acts aas a step-up transformer, and will give you 
something a bit less than mains voltage across what was originally its 
primary winding. And of course that's totally isolated from the mains.

If you manage to get a transformer designed for 230V mains for the second 
one (or one with 2 115V 'primaries' that you can connect in series), then 
just rectiying it would probably be OK for the nixie tube supply. If you 
can only get one with a single 115V primary, you could use a voltage 
doubled rectifier. Either way you'll end up with something over 300V DC

-tony