I bought this for my system rebuild to make it quieter. I can't get the system to turn on. If I hook up the old power supply, the system comes on.
My confusion lies in the three four pin connectors for the mother board. There is one sleeved with the main mb power cable, and two on their own lead. For the two on their own lead, one is marked 4+ and the other 4P. Neither works.
It's a little tricky because I'm using a 4 pin extension, and I can put the 4 pin connectors in the extension in a couple of ways.
Also, how do I test the power supply to see if it works at all?
For the two on their own lead, one is marked 4+ and the other 4P. Neither works.
Either one could work, but the motherboard normally accepts only one. I hope your extension doesn't allow reversing 12V and ground. If it's connected properly, then it's defective or not powerful enough.
To test it, disconnect the PSU from the system and power it up (http://www.techpowerup.com/articles/other/22). Use a DVM to check voltages. The problem is that you'll be checking a PSU with no load at all, therefore it isn't a very good test.