How to test a Mac Pro PSU


I have an early MAc Pro (Original) that I suspect has a faulty PSU. I now that the simplest way to test would be to swap with one that works but I dont have access to one. DOes anyone know how to test the PSU. I cannot find specs for the voltages on the PSU connector anywhere. Also I have access to a Mac Pro (early 2008) but I am not sure if I can just pop this PSU in the MAc Pro original. Does anyone know? Also I believe that it may be possible to use a 3rd party PSU but again I cannot find any details on how to go about dong this. Any help greatly appreciated.