Nixies, was Re: Octal

[Tony Duell]

> > I would seriously recomend against rectifying the mains for something
> > like this. Non-isolated PSUs have the nasty habit of making things live
> > that you least expect, and may kill you (or worse, damage a classic
> > computer).
> 
> Oh,  I wasn't suggesting that,  simply pointing out that once you got your 
> isolation a simple rectifier would do the trick just fine...

Depends on the turns ratio of the transformers...

> 
> I've had my experiences with non-isolated equipment,  more than I ever wanted,  
> and don't plan to build any to add to that.  :-)

Me too. I grew up fixing series-string radios and TVs (until the coming 
of 'baseband' audio and video sockets, such as the SCART connector, most 
TVs sold in the UK, even semiconductor-based ones, had a live chassis). I 
don't much care for working on such units.

What amazes me is that in the 1950s and 1960s, UK magazines published 
several educational courses. Typically you'd start by building a crystal 
set, then turn it into a 1-valver (leaky grid detector), then add audio 
stages, RF stages, and maybe end up with a superhet.

Thing is, you got the HT (B+) by half-wave rectifying the mains. The 
exposed metal chasis was connected to mains neutral. And you had 
headphones. You know, that could easily turn into an electric chair...

> 
> > If you use back-to-back transformers as I've suggsted, the actual voltage
> > got get out depends on the turns rations, of course. Maybe a simple
> > rectifier will be enough, maybe you need a doubler.
> 
> Many suggestions that I've seen illustrated like that suggest using two 
> identical transformers,   which should get you the same thing out as you put 
> in.

YEs, but there's no _requirement_ to do that. 

-tony