Well that didn't last long. The second-hand 2008 (3,1) 8-core 2.8 GHz Mac Pro I bought a month ago has decided isn't going to start up any more.

Pressing the power button, it comes on for about a second before switching off. Searching various on-line sources indicate that it's probably a PSU fault, but it could also be a motherboard failure.

I've done most of the tests that I could find on-line on power up I get the memory LEDs and and graphics card present LED on the motherboard illuminating. Pressing the motherboard test button indicates the presence of the trickle charge but nothing else.

I've looked but can't find any information about what voltages should be present on the various PSU pins so I can see if it's a PSU failure and perhaps worth replacing or if the PSU is OK and motherboard has died. Can anyone tell me or point me at a resource that does have this information?

Thanks!

http://pinoutsguide.com/Power/apple_mac_pro_psuj3_pinout.shtml

Any help?

Thanks, looks like it only covers the two models before mine though.

It does cover the Mac Pro 2.8GHz Xeon (A1186) - Early 2008 MA970LL/A - which I think is yours.