23 Jun
1997
23 Jun
'97
1:50 p.m.
Tony,
> > Center tapped ransformer is used. Both 17v ac at 2amp each on each
> > outmost pins, center pin is the center tapped wire for transformer.
I vaguely remembered had to run up the power card with
dc
transformer so I could puzzle out last one or two voltages on it.
Had to do several steps to find all the voltages.
From there, wired up a adapter which worked. Note, it is not 24vac
on each line! it is 12v on each wires if you buy center tapped
transformers you will see like that added up by outside two wires
measured. It goes like that marked on the transformer and the
transformer has three wires, of two wires same color and one is
different color, then it's a center tapped.
I'm not sure I understand that at all. I assume you're saying that it's a
12-0-12 trasformer (or actually 17-0-17 - I am _sure_ 17V is mentioned
somewhere in the IBM manual).
Do you agree with the circuits I've just sent out? If not, could you
please tell me where I've gone wrong?
Hello? Knock, knock...:) Anyway I did clearly
remember that 17v ac
Yes, I'm here...
on each wire (of two) and the center tap on one
wire.
The power card rectify and regulates all the voltages for the
Yep, I'll agree to that.
computer. That sort of thing I did build several
power supplies
based on center tapped transformers, using center tap as common.
Consider this: Take two aa battries and wire up in series, total
voltage is 3v assuming they're fresh. But put a wire as common
between two batteries and measure two wires in turn without swapping
those probes! This will give you one positive 1.5v and negative
1.5v which that how center tapped transformer power supplies in this
Yes, that sounds 100% reasonable. I may be from Cambridge, but I do
understand _some_ electrical engineering :-) (Seriously, I had to explain
jsut that to a 3rd year student in electrical engineering the other
week..... There is something wrong with the world.)
After all 'There is no such thing as ground' What you take as a 0V
reference is entirely up to you.
configuration worked. But part of the circuity
requires components
to rectify and smooth out the ripples caused by ac to dc
rectification process then final voltage regulation to complete the
inefficient ac to dc conversion process.
The inefficiency in a linear PSU is in the regulator (which wastes energy
as heat) and not (in general) in the rectifier or smoothing circuit. Of
course a high-frequency SMPS can get away with smaller smoothing
capacitors and a smaller (ferrite-cored) transfoemer.
Efficient power supplies are switching type, little heat
and low losses in conversion process plus very light weight.
But they use same design in outputs (secondaries but for some who
knows electronics, these uses high frequency or fast recovery diodes)
See my comment on that crazy Zenith PSU that I mentioned in an earlier
post....
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill