Mac Pro Early 2009 turns on, then turns off after 20-30 seconds

[APTheHunter]

I’ve been tying to fix a 2009 MacPro4,1 dual Xeon for a while, and the problem is: it turns on for a bit, then clicks off, and won’t turn on again for a while. If I leave it for maybe half an hour it will come on again for 5-10 seconds then click off again. The PSU has been replaced and the thermal paste on both CPUs and Northbridge have been replaced in attempts to fix it, everything else is stock. Does anyone have any tips on how to fix this? All diag lights are normal, the button cell battery is fresh, and taking out or putting in various parts (HDD, ram, disk drive, GPU) doesn’t make a difference. Anyone have any advice on how to fix?

 

[Cory Cooper]

Hello and welcome.

Initial thought is there may be an issue with the logic board. Do you get the startup chime? Does the Apple log appear with the progress bar at all?

C

 

[APTheHunter]

Hello and welcome.

Initial thought is there may be an issue with the logic board. Do you get the startup chime? Does the Apple log appear with the progress bar at all?

C

It turns on for less and less, but a while ago it would stay on long enough to get to the progress bar. Now it can only get to the startup chime, but it does that successfully.