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I just got an old AT PSU from a guy. I want to test whether it works. I plugged a hard drive on it and plugged the PSU in the outlet, but it won't turn on. I know that ATX PSUs need to have two wires twisted up for them to power on, but I thought it wasn't needed for AT PSUs? Is there something I need to do for it to power on or should I declare it dead?

Picture of the PSU :

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migrated from Jul 19 '12 at 14:25

This question came from our site for electronics and electrical engineering professionals, students, and enthusiasts.

Wow, be super careful, the insulation has slipped off some of the wires Bruno mentions and that is at mains voltage! – gnibbler Jul 18 '12 at 0:29
Yes you are right, I put the insulation back on right after I noticed it on the picture as I was posting it. – user922764 Jul 18 '12 at 0:48
up vote 4 down vote accepted

The female connectors at the end of the black cable must have been connected to a double switch. You need to connect them together.

I can´t tell you which should connect to which, but my guess is brown - black and white - blue.

But don't take this for granted, if you have a multimeter check which are the wires that connect to mains plug and make sure you don't connect them together.

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Someone else told me to do the same thing after seeing the label on the top of the PSU. You were right! I connected the black and the brown wire together and the blue and the white wire together. I plugged the PSU and it powered up! Right now they are well taped together and isolated using electrical tape. – user922764 Jul 18 '12 at 1:00

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