[sdiy] Power Supply ???

[John Blacet]

If the current draw on the 5V line is small, it would be better to sub
regulate the 5V from the regulated +15V or +12V or whatever than trying
to drop the 20V in a regulator. You can also use a smaller "L" type
regulator for this if you need less than 25 mA or so. Another trick is
to use a series resistor to drop some of the voltage pre reg. This works
fine as long as the current draw is fairly consistent. You want a
minimum of about 8V into a 5V reg.

Naturally, you want to check the resistor and reg for heat.

Regards,
--/////--
John Blacet
Blacet Research
http://www.blacet.com