More on Fav Designs - switchmode power supplies

[David Halliday (Volt Computer)]

My original point was that these were *NOT* suitable for use.
They are tempting - cheap and should be easy to rework but they radiate
noise like a small sun...

I tried using a larger computer power supply for my own setup at home
and the increase in background noise was profoundly audible. ( can you
say Niagra Falls? )<grin>

Maybe reworking the unit - adding better filtering and regulation - is
an option but would probably spend more time with this than you would
building a decent regulated analog supply from scratch.

> -----Original Message-----
> From:	av599 at lafn.org [SMTP:av599 at lafn.org]
> Sent:	Saturday, April 19, 1997 8:22 AM
> To:	synth-diy at horus.sara.nl
> Subject:	More on Fav Designs - switchmode power supplies
> 
> >> [Dave Halliday]  I think that the question is more one of using
> >> computer surplus supplies and these have been designed without
> analog
> >> considerations.  With PC Clone supplies selling for $20 new, it
> would
> >> be tempting to be able to re-work one of them to give +/- 15 volts
> at
> >> a couple of amps - maybe a good design project...
> >
> >Is this feasible at all?  I'm philosophically very
> >much in favor of gleaning what ever we can from the mass
> >manufacturing machine; let it work to *our* advantage once
> >in a while.  Since they're cranking out enough of these
> >things to make them dirt cheap, it'd be excellent if they
> >could be adapted to our purposes; even if that adaptation
> >is a little convoluted (I think I have a couple of blown
> >PC PSs in my basement right now).  Or would one still
> >spend more in the process than on a from-scratch approach.
> >
> >steve - the scavenger!
> 
> All you have to do is find the +- 5 volt supply windings on the
> transformer. Usually it's only a couple of turns. Rewind it for
> whatever
> voltage you want and change the filter caps' for ones with the new
> working
> voltage. The new windings can be snaked through the ferrite core
> without
> much trouble. The supply remains regulated because of the feedback
> winding
> being independant of the +- 5 and +- 12 volt windings.
> 
> Hope this helps some.
> 
> Doug
>