24 Jun
2013
24 Jun
'13
5:36 p.m.
On 6/24/2013 3:01 PM, Tony Duell wrote:
Above all, the design has to be very safe. Even
if it's put on the net
as a "You build it at your own risk", it's still a liability. And, I
have to consider the many ways people will try to mess it up.
Appreciate the ideas. I like the idea on the dual secondary windings,
etc. I am just not comfortable designing it myself. I can do it for
myself, but I really want someone (or some company) who does it for a
living to design it, whatever it ends up becoming.
Jim
Why? Efficieincy, or is there some other reason?
Efficiency, primarily, and the implications (smaller size, runs cooler,
hopefully last longer, etc.)
Actually, I tend ot do tthe design and if you
don't like the price,
that's your hard luck. Building down ot a price is what has casuedd me a
lot of probles. Certainly if I was making such a supply it would const
considerablly more (some years ago I mand an unregualted 6V PSU for a
client. Byt the time I had finished, the components had come to over
\pounds 100.00. That did nto cover my time in making it either.
Transformer,s cases, etc are not cheap.
Well, some in the community would argue
that finding a way to make a
$200.00 PSU for a vintage PSU is not really a solution, as anyone can do
that, by buying premade PSUs and putting them in a large enclosure.
What I would do is start with a 100VA transformewr
with 2 separate 9V
secodnary windigns. That is a standard transfomer. Get one with a pair
of 115V primaries and use the standard selector swich circuit to connect
it for 115V or 230V mains.
I am sure a design firm would take that route, and I
would not turn away
a design like at this time.
One of the seondaries is used fro the 9V AC output as-is.
The other one is rectified, smoothed, and fed to a simple switching
regulator to bring it down to 5V.
Incidentally, this is basically the circuit of the C128 power brick (at
least the one I have).
Yes, it is.
I think you are going about it the wrong way. Given that that 9V AC can
be used for almost anyting, I think you want a reasoanbly sinusoildal
wave. And to produce that from 5V DC is not trivial. It can be done, but
heck, you've got AC mains around. Just use a transformer.
In practice, no one
uses the 9VAC on the 64 and VIC as AC. It's not on
all user ports, so systems don't plan on it being there, and the
cassette port uses it only after being shunted to 6.3V or so. The
square wave harmonics are what bothers me.
But, I thought as you did. Get the 9VAC at 45VA, and rectify the 5V out.
But, I am having a hard time finding a suitable base PSU to buy.