How to build a undependable voltage supply?

I want to build a variable voltage supply (maybe 2) I want changeable AC voltage and Variable DC voltage. Mainly I want to make a unstable DC voltage supply. Does anyone have a schematic I can run off of? I'm also looking for it to be CHEAP, I don't want to spend more than I don`t know $30 on it, preferably less. Anyone enjoy any good ways for me to build one?


Answers:    http://www.electronics-lab.com/projects/...

This should fit the bill. If you look at surplus dealer you may be able to find it down to 30 bux

The ac supply is more difficult. A variac transformer is the usual way we would do this. Maybe you could amend one of these designs

http://www.ibiblio.org/obp/electricCircu...
go to radio shack and buy one. I usually don't suggest spending money when you can do it yourself, but, in this covering it will be cheaper and work easier.
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