MacPro 3.1 does not start up

hi, laudou, johnb-one here, putting in my 2 cents.... as requested by Mr. Bennet-Alder. He is quite correct.... what you have to do is, in essence, strip the Mac Pro down to its essentials.... BUT....... to know how to do that, you need the Mac Pro Technician's guide for the 2008 Mac Pro (the 3,1)...it's available at https: //tim.id.au/ laptops/apple/macpro...you got your Mac Pro technician guide for the 2008 Mac Pro, the 2009 Mac Pro and the mid 2010 one.... I suggest you follow the official guides (they're in .pdf format) so download 'em, read 'em and away you go !! you also might want to check out iFixit.com and greggant.com, plus there are a few videos on Youtube about the Classic Mac Pro, plus there's a couple of Facebook Groups for Mac Pro's of all stripes, 3,1....4.1 and 5,1 (the one I have) , if you're into that as well....asking questions....asking for help...posting tips, friendly forums....that kind of idea.....there are also a number of diagnostic LED's towards the inner front, in 2 rows going down, just inside and towards the top of the Mac Pro.... some of those LED"s light up as the Mac Pro starts up....others you have to press a little tiny button around there to get 'em to light up..... in addition, there are various other LED's scattered around the inside of the Mac Pro to indicate certain conditions or problems.... they all tell you something important, they all indicate something....whether good or bad.... again, laudou, follow the Mac Pro tecnicians' guide I mentioned from tim.id.au....etc... which defiinitely has something about the LED's in there and what they mean/indicate/show... It also has a handy dissasembly guide...and tells you the tools needed to accomplish that particular task or set of tasks..... and how to go about doing it.... As was also mentioned by Mr. Grant-Bennet-Alder, power supplies do get hot and have high parts counts... especially when said power supply is clogged with dust, crud and fuzz and isn't able to get adequate ventilation or dissipate heat that well... Diagnosing and repairing a power supply is a task usually best left to a PC repair shop or a really good electronics repair shop that specializes in such repairs.... Usually if you have a known dead /stone dead power supply and all other causes have been absolutely ruled out, then the best option is to replace that power supply which isn't that hard to do..... getting the power supply's connector/plug to the main board (*the logic board) disconnected and re-connected is a real bear, but it can be done, the same with removing the old power supply and installing and connecting a newer known good working one... again, it's a bear, but it is possible if you are patient, careful, and follow the guide.... replacement power supplies could be found on eBay.... if you are 100% sure that the power supply is not working correctly/stone dead. In answer to your question "Could both cpu's have died at the same time ?"....Yes, I suppose that is technically possible....but I haven't heard of it happening frequently and haven't experienced it myself. Usually it could be another component or board (*either the ram riser board,(s) or another board, or something else) before both CPU"s could and would have died at the same time.... i'd say it's a pretty rare occurence, but it have been known to happen now and again..... how often ??? Not very.... About the only source for spare parts for your Mac Pro 3,1 (The 2008 model) would be a store or website that deals in/specializes in /sells used Mac Pro parts.... there are some out there.....somewhere.... I suppose if you looked really really hard,. you might even be able to find parts for a Mac Pro 2,1 or 1,1 ....but that's stretching things a bit too too far...yes ???

good luck and I hope this has helped you, not overwhelmed you or blown your mind too much... or given you "Information Overload"..... just something to get you going, get you started, help you make some progress....and maybe learn some stuff while doing so... heck, you might even say it could be fun.....maybe a challenge.....

Anyways, laudou, I'm no Mac Pro expert, didn't /don't have any Apple training, not certified to do anything....apart from maybe make coffee.... I have nothing to do with Apple at all. I'm just a Mac user here, same as you...maybe the only difference here is that I've been using 'em since about 1986..... yeah, that makes me an old goat.... that's about it, really.....

anyways, good luck, laudou....I'm off for a while to enjoy my coffee , etc....

John B

Then, based on your experiments so far, your power-on button looks to be OK. Your power supply works in another Mac, but I would feel better if you saw the PWR ON indicator light up.

I think that leaves components on the mainboard. Before you tackle that, are there any other steps in the manual that suggest other things to try?

To get the mainboard out to look at it means getting involved in heatsink compound, because (if I recall correctly) the heatsinks and processors have to come out before the board can be removed. Are you geared up for that? (new heatsink compound an a long-handle or T- wrench to remove the heatsink bolts?)

Your symptoms correlate with dead standby battery. Anything under 3.0 Volts is used up.