PC Power Supply for Arduino based CNC machine- How to bring it to life?

Hi everyone!
I am currently working on an Arduino/Disk Drive based CNC machine.
For this project I wanted to salvage an old PSU from a PC at school.
I think it’s an ATX with 20 pins.
After reading topics on the internet about this kind of project, i tried to connect the green wire (PSU-ON) to Ground, but it only power for a short second or so and turns itsself off after this.
Even with a Load on the 5V Line (An old Disk Drive) it doesn’t work at all.
So I tried to connect random wires, trying not to short something.
When connecting the purple wire (SB 5V) with a slot in which a brown and an orange wire go at the same time, it powers on and the Fan starts spinning.
The problem is:
The PSU only puts around 4.8V out on the 5V rail and 3.5 on the 12V.
Even connecting my Load to it doesn’t help. :slightly_frowning_face:
I can get the fan to spin faster and push the 12V up to 5.1V when connecting the brown and orange wired slot with 5 or 12 V. Any idea what mistake i am producing? Or is the power supply broke?

Many people have done this. Do not just crash around.


Tanke you for your reply! I'll try a different load. I only did this with the DVD Drive because I read in another instruction. I'll tell you whether it worked.

Okay, I just hooked up a small 5v 6W light Bulb to the PSU, while connecting green and black connections.
No differene at all. The Bulb lights up for a brief second and turns off.