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12VDC from computer power supply WHILE COMPUTER IS RUNNING? Answered

Okay, how crazy would this be?

I need a 12VDC power supply to do some bench testing. I have a computer by my workbench which has at least one free Molex connector coming out of the PSU. I know I've seen Instructables that show how to make a bench power supply from a disconnected computer PSU, but would it be a really terrible idea to run wires out the back of the computer case to my bench and use them to test circuits?

What are the potential pitfalls, and what are some steps I could take to make them less likely? I'm thinking fuses on the incoming power lines are the first step.


Good advice. I'll pursue other options. Thank you!

Let me tell you a story.

Back in 2002 i was messing around with my PC, changing locations of fans and re-routing power cables to the fans while the system was on. Everything was going fine till one of the fans i was adding to the system was plugged into the PSU. As soon as it was plugged in the PC died. The PSU itself was fine but the sudden surge on the power line killed the motherboard.

There is nothing you can do to prevent such an occurrence. A bench top power supply needs to be resilient because mistakes are going to be made. Even if a mistake isn't made if there is an instant spike in the power being pulled from the item you are working on it can kill the PC. SO do yourself a favor and find an old PSU from an old PC or buy a cheap $40 one from somewhere.

Just get another computer PSU. The cost of a new PSU vs a new computer if you do something silly is not worth saving the small amount by not buying one.