ATX bench power supply (alternative)

[Cliff Matthews]

Since ATX bench threads seem to go on forever, I suggest someone (with more elegance than I) post a single prominent sticky titled "Good Non-ATX bench power supplies for novice builders"
The very act of having that title should cut down on ATX thread clutter and provide newcomers with quick, solid candidates for bench supplies. (and please, I mean no offense to anyone)

A possible candidate: Ink-jet printers are common "reusable refuse" from the computer camp, and I've not seen suggestions yet for using one or two (~28 to 32 volts DC @ 600ma to 1.5amps) to feed classic 317T/337T pairs for something
Simple, Safe and Silent.

On many, the outputs are unearthed, so outputs can be coupled for split pre-regulation (up to 64 volts). Add  a resistor and 2 series diodes to each rail and you have the reference for the regulator on the other rail.
Even if 2 plastic supplies have mains ground pins, don't use them. Instead mount and couple them inside a grounded enclosure (with fuse and switch) making sure to isolate the rest right up to the binding posts.
For those that like that rough "ATX supply look", install a couple of 24v universal laptop adapters inside like this one http://www.ebay.com/itm/96W-Universal-Power-Charger-Adapter-AC-110V-240V-For-Laptop-Notebook-EU-Plug-SC-/251793362315.

I suggest using an LM7805 to feed the fan with a pot on the adjust pin to vary it between 5 and 12volts (those regulators will need cooling). - Cheers!

[jeroen79]

These still have the drawback of not having an adjustable current regulation.

If you do something wrong then such a powersupply will let as much current as it can supply run through your circuit.
Even if this is not as much current as an ATX PSU it may still damage your circuit.

[Cliff Matthews]

These still have the drawback of not having an adjustable current regulation.

Fortunately LM3xx's are cheaper than crackers. Pass juice through a few power resisters via switches for the higher currents, and route through a wire-wound pot (say a hundred ohms) for the lighter circuits. You loose 1.25v but as long as a budding hobbyist gets 25v out to the posts for $20, they're doing OK.