IBM PCjr

From: jpero_at_mail.cgo.wave.ca <(jpero_at_mail.cgo.wave.ca)>
Date: Mon Jun 23 11:42:54 1997

Tony,
>
> 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).
Oh, It was just a unloaded probing run to figure out what voltage is
there because my reference is all screwed up. Actually did it with a
regular small transformer not those center tapped ones.
Sorry.

> Do you agree with the circuits I've just sent out? If not, could you
> please tell me where I've gone wrong?
>
Yours is fine. :)
> > Hello? Knock, knock...:) Anyway I did clearly remember that 17v ac
Don't take as a poke, I was just in jest, good mood. :)
>
> Yes, I'm here...
Whew.
>
> 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.)
You got my ears peaked up. What was that trouble with this 3rd
student's error?
>
> After all 'There is no such thing as ground' What you take as a 0V
> reference is entirely up to you.
Really? Common, ground, 0V, neutral, power return makes my mind spin
but I adapt to what you're talking about...so you're not talking
mumbo-jumbo stuff. :)

>
> 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.

I know about this linears heating problem and I do have a old Asus
P/I-P55TP4XEG pentium which has one on board. HOT as sun and must
air-forced cooled on it keep it bit warm not hot. :) But my Asus
P/I-P55T2P4 rev 3.x new board now uses switchers on it and they use
tiny heatsinks and stayed cool even they're able to channel 10amp
through them. Impressive. And more IMPRESSIVELY is that Asus's new
VX and TX boards uses these SMT switchers without any heatsink,
relying on ground planes to spread heat out and radiated off.
Why I had to get new one? Old XEG I/O chip blown by static
accidently but I removed that SMT 100 legged IC and it worked again
for other purposes for now.

>
> >
> > 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....
Done and replied! :)
 
> --
> -tony
> ard12_at_eng.cam.ac.uk
> The gates in my computer are AND,OR and NOT, not Bill
>
Jason D.
Received on Mon Jun 23 1997 - 11:42:54 BST