5 Sep
2006
5 Sep
'06
2:27 p.m.
On Monday 04 September 2006 07:12 pm, Tony Duell wrote:
Depends on the turns ratio of the transformers...
I've worked on my share of that stuff as well, and I don't care for it
either.
YEs, but there's no _requirement_ to do that.
True.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
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... 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...
I'm not familiar with mains wiring there, is the connection in any way
polarized? Lately I've been running into those stupid polarized plugs here,
but there are still numerous extension cords and outlets that don't have the
wider slot and there's no guarantee of them being wired properly anyway, so I
usually end up having to fix those with a nibbling tool for them to be usable
at all. I don't understand why they didn't start out with a polarized setup
in the first place, if one wire was supposed to be grounded.
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.