250mw PSU 650nm laser "blinking" help

Building my first laser, 250mw i know is a lot to start with, but I want to burn stuff. I have it assembled and connected to a power supply from a desktop computer. Every piece of the laser minus the PSU is brand new.

Problem:
When i plug in the power supply the fan goes on inside the supply but not the laser, then when the fan turns off the laser turns on. The laser seems like its blinking as if it's got low batteries. The fan will come on again and the laser turns off. Help!?

Without more info we can't really help you any.

Are you saying you wired a red laser diode directly to a computer power supply or that you wired the driver for your laser to the power supply? You NEED a driver.

Which voltage rail did you connect the laser (module?) to? Did you provide the minimum load needed on the 5V rail for the power supply to energise? Computer PSUs require a load on the motherboard connector for it to truly turn on.

yes i connected it to e module, i wired the green/black wire to turn it on. I basically followed the laser hack on youtube with the power supply, except i replaced the driver with one from amazon which is the one recommended. I have no idea if i've supplied the minimum load. The beam turns on, just very weak.

Well, I don't remember the ATX color coding any more, but there is a thread in the Geek's Corner here that has all the info you need:

http://laserpointerforums.com/f60/pc-psu-into-lab-psu-64220.html

Just follow that as far as getting the PSU to stay on at full power, and hook your module up to the correct rails, and you should be fine as long as the module is correct for the diode, wired and set correctly, and is supplied with the correct voltage.

IIRC if you don't load the rails correctly then when trying to power something the PSU loses regulation and will not put out the correct voltages at appreciable power levels.