How much current do you need?  If you have an AC output wall wart you
may be able to run a capacitive voltage doubler on the output to get
at least close to your requirrement.
More than a few 10's of mA however & the cap sizes required become very large.

RP

On 02/08/06, Russell McMahon <apptech@paradise.net.nz> wrote:
> >I need an approx. 48Vac (rms) source for some quick testing.  So I
> >open
> > an adjustable DC wal wart, remove the capacitor, but found the
> > maximum
> > tap I could get was about 24Vac.  As it is a 240Vac line here, and
> > there
> >  is an option to switch the line select to 110Vac, I gave it a try
> > (actually 2 tries to burn 2 transformers).
> >
> > With no load, the transformer burned out few second later.  The iron
> > was
> > hot, and the primary side seemed to be burned out as it was measured
> > open.  I could not cut through the paper to see what had burnt last
> > night as they were hot, but they are gone now (thrown off).
>
> Given two supplies you could have run both and placed their
> secondaries in series.
>
> Failing that a little magic and playing with some L's and C's would
> possibly give you what you wanted.
>
> If you had anything else with a 2:1 winding ratio and a lower winding
> voltage >= about 20VAC you could have used that as a 2:1 stepup
> transformer.
>
> Excessive voltage will increase the nmagentisation current which will
> saturate the core which will drop the primary inductance which will
> ... :-(.
>
>
>
>    Russell
>
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist