Is it possible to wire computer PSU's in series to achieve a higher voltage? If so, how can it be done?

I want to make bench top PSU's out of old computer power supplies and I want a 24v output as well as the typical outputs, but I don't want to put a transformer on it that could only handle so much current (I might want to run some bigger motors off it)

The easiest way to achieve the desired result is by taking the ground (black) wire from the output of one power supply and connecting it to the +12 v. (usually yellow) on the other. Unfortunately, not all power supplies are totally input voltage/output voltage isolated. You could very likely end up with a 12 v. potential difference between the 2 cases.
If you're decent with a soldering iron, it would be easier to trace the yellow lead back inside the case to the rectifier pair and put a polarity opposite pair right alongside. DO NOT open the case on any power supply before disconnecting the AC cord from the wall and allowing the input voltage filters to bleed off. The filter caps in the PS I just opened are rated for 200VDC. This means they will probably have 150 - 175 DC when active which jives with reality. Under proper (or improper) circumstances, this voltage can be lethal. Verify the correct rectifier pair with an ohmmeter on Rx1 (make sure the AC has been disconnected for at least 10 or 20 MINUTES).
You will also need a heatsink for the second diode pair. The amount of power this heatsink will dissipate will be 1.4v X output current = dissipated power in watts. One equal in size to the original diode pair's sink will be fine since your total output current per each will be halved.

This will give you + 12 and -12 at half the total +12v current rating, but now the case will be floating halfway between the two.
Happy soldering!

The Ideanator (author) 8 years ago
Ok, done.
The Ideanator (author) 8 years ago
Seems easy enough, thanks. I'm gonna try it.
The Ideanator (author) 8 years ago
You could draw it out in a paint program and upload the image, I'm thoroughly confused with the ascii based diagram