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I don't know what you mean by 'jump the PSU' But , you can buy Voltage testers to check output at various terminals. Or just try another PSU in yor current machine to see if that really is the problem.
I know what you are talking about. You can jump 2 wires together outside of your motherboard to get it to run, because it won't run unless it is supposedly hooked up to your mobo. I'm not exactly sure which 2 wires you jumper, but I know it can be done. Let me look around a while and see if I can't find it for you.
BTW
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Edit: Have a look here and that should be all you needed to know about jumpering a PSU to test outside a mobo.