Mac Pro 3,1 power problems

Sorry in advance for the novel.

I have an A1186 3,1 Mac Pro tower that I have been having a lot of issues with. For some reason i would go to start it up and would get no chimes, just loud fans. If I waited a few minutes, It would occasionally chime and start up, and I could work with no problems. I assumed it was a power supply issue, so when I got sick of dealing with it I bought a replacement and installed it this week. It started up perfectly the first time I plugged it in. Chimed immediately and I worked for hours with no problems. After putting the Mac to sleep and coming back the next day I had trouble getting it to turn on again. When I would press the power button I got no chimes, no fans- nothing. After a minute or two of finagling I pressed the button and it started up. Again worked for a few hours with no problems and then I shut it down. When I can back today I went to turn it on and had the same issue. No lights, no fans, no chimes. Totally unresponsive. Now it's been twenty minutes of messing around and I'm heated! I've tried with the old PSU, the new, new power cables, no graphics cards, no ram, no hard drive, every which way and I can't get anything out of it. When I plug it in I can see a very dim power light above the button that I wouldn't be able to see with a light on in my room, but it is unresponsive.

Could it be possible it's another failing PSU?
With my luck, I wouldn't be surprised.
It just seems unlikely.

Welcome to our forums.

I suppose you could have had a run of bad luck and received a bad PSU. Can you return it and get another? Also, how about trying another graphic card? Do you have a spare?

I'm trying that now- it came from a working Mac though. I have two graphics cards in it. I have tried with both of them, each of them, and neither of them with the same result. Absolutely unresponsive when I press the power button.

STBY led shows yellow when I press the button inside. No other lights are showing. Could it be a problem with the power button itself?

I don't think it's the power button, but you can never tell. You could try bypassing it by shorting it out, but be careful! I would also try returning that PSU and exchange it for another.

Problems with the PSU would be my best guess as well. And like chscag mentioned...the replacement PSU may have had problems (rare, but can happen).

By the way...was this replacement PSU brand new or used?

- Nick