Help connect 2 PC power supplies in series 24v

[electr0n]

I've got two identical pc power supplies that I'm trying to connect in series for 24v. Each one works fine when used by itself at 12v but when I try to connect them in series one of them shuts down. I cut the ground wire on one supply and have them so they're not touching each other. Anyone know why it's not working and what I can do?

 

[electr0n]

I'll answer my own question. I found a very good tutorial http://www.procooling.com/index.php?func=articles&disp=52&pg=1. Despite cutting the ground wire from the outlet, the negative on the output was connected to the case which was causing a short. Removing the circuit board from the case on the non grounded supply got it working.