[sdiy] Power Supply Question

[Scott Gravenhorst]

"Ray Wilson" <raywilson at comcast.net> wrote:
>Does anyone have a circuit idea (schematic, web-page, etc) that shows how to
>use a wall wart to get a + and - 9V supply at about 50 to 100 mA per side?
>Do they make dual supply wall warts? Do they make wall warts with center
>taps?
>
>Any help appreciated.

Wow, what a relief from the analog better, no digital better, no vinyl
better, no CDs better...  I broke my delete key on that one.  Whew.  So thank
you for this,  a REAL SYNTH-DIY question!

I've not seen center tapped wallwarts, but I suppose they could exist.

The current demand you need isn't large, so you may be able to do it by using
two halfwave rectifier circuits from one non center tapped wall wart.  This
is exactly how it's done in the FatMan (see schematic at www.paia.com).  In
fact, the FatMan supply has 3 regulated outputs for +5, +8 and -12.  One
halfwave circuit provides that + raw voltage, so it's diode will be one way,
the other diode which is reversed will produce the negative raw supply.  The
other transformer conductor is the system's common or ground.  You'll want to
make sure the filter caps are big enough, but again, 100 ma isn't that much
and should be easy to do.  In the case of the FatMan, as 12 volt transformer
is used.  I think you'd want to find a 9 volt transformer, and you'll want to
regulate the output voltages.



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