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MP 1,1-5,1 Mac Pro 5,1 powers ON for a second, but quickly shuts off.

tripmusic

macrumors 6502
Original poster
Oct 26, 2012
395
58
Switzerland
So a while back I was having problems with my Mac Pro 5,1 (flashed), basically it went dead. I replaced the PSU, but it didn’t fix it, but then I replaced the motherboard and all has been well for a couple months.

That is until the other day, when it just shutdown whilst running and wouldn’t power on and boot again. The power light comes on for a second, but quickly shuts off. I get 5V trickle and no other diagnostic lights are on, on both the motherboard and processor board.

First I swapped CPU’s and still wouldn’t power on. So, I broke it down into minimum configuration and was able to get it to stay on with the CPU out of socket. I put a CPU back in and was able to boot up. So I cleaned the CPU and heatsink and applied new thermal paste and it was working last night and I left it plugged in overnight. Then today I try to power on and no go. Power light comes on for a second and then it shuts down. I tried minimum config with no CPU again and it won’t turn on. I left it unplugged, went to the store for an hour and when I came back it turned on in min config, but then a few minutes later no power again.

I’ve tried different AC plugs and mains outlets as well. I’ve run ASD and the only error I get is a voltage sensor in SATA bay 3 (see attachment), but I’m not sure that’s causing the problem because I’ve disconnected the SATA cable to the motherboard when in minimum config and no difference. I’ve had this error since I put this replacement motherboard in and it was working fine.

My Northbridge rivets are OK, though one did pop through a while back, but the Mac Pro was working fine even when it was loose and once I got the rivet back in place. Northbridge temps have been 60c at idle and 70c under load.

I’ve noticed the CPU over temp light flashes after a few seconds when it shuts off. It did this last night after I shut down after having it on for a few hours. I remember this light flashing on shutdown in the past when my older motherboard was on it's way out. When it’s working fine, the light does not flash upon shutdown.

So I’m stumped and I don’t really want to spend money on the wrong component. It either has to be the motherboard or processor board, as I know I have two working PSU’s. I’ve attached the ASD SATA error and videos of it’s behavior in minimum configuration.

TL;DR: Intermittent Powering ON and boot. Shuts down after Power button pressed in min configuration. See first video.


No Power ON, quickly shuts off in minimum config


Power ON OK in minimum config

ASD SATA Voltage Error
ASD SATA Voltage Error.png
 
Last edited:

tsialex

macrumors G3
Jun 13, 2016
8,354
8,867
I honestly tried to read your post, but got me a headache. Please use paragraphs and separate your ideas, no one decipher blobs of text for free.
 
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tripmusic

macrumors 6502
Original poster
Oct 26, 2012
395
58
Switzerland
I honestly tried to read your post, but got me a headache. Please use paragraphs and separate your ideas, no one decipher blobs of text for free.
Sorry about that. I will try and clean it up. If you watch the first video, that should show you what's going on without having to read anything.
 
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tsialex

macrumors G3
Jun 13, 2016
8,354
8,867
When you can't power your Mac Pro on, if you press the DIAG button, what LEDs are lit?
 
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tsialex

macrumors G3
Jun 13, 2016
8,354
8,867
2nd paragraph, 5V trickle
This is very weird, even a backplane without the SPI flash/BootROM shows the LEDs below lit:

  • PSU PWROK (green)
  • 5V STBY (amber)
A normal working board without an Apple OEM GPU should have these LEDs lit:

  • PSU PWROK (green)
  • 5V STBY (amber)
  • EFI DONE (green)
 
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tripmusic

macrumors 6502
Original poster
Oct 26, 2012
395
58
Switzerland
This is very weird, even a backplane without the SPI flash/BootROM shows the LEDs below lit:

  • PSU PWROK (green)
  • 5V STBY (amber)
A normal working board without an Apple OEM GPU should have these LEDs lit:

  • PSU PWROK (green)
  • 5V STBY (amber)
  • EFI DONE (green)
Yes, but you'll only get those when it actually powers on? I get all of those and GPU OK (even with no GPU installed) "when" I'm able to get it to power on and stay on. I can't get those LEDs if it won't power on. When it's shutdown, 5V STBY.
 
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tsialex

macrumors G3
Jun 13, 2016
8,354
8,867
Yes, but you'll only get those when it actually powers on? I get all of those and GPU OK (even with no GPU installed) "when" I'm able to get it to power on and stay on. I can't get those LEDs if it won't power on. When it's shutdown, 5V STBY.
To get GPU_OK lit, you need an AppleOEM GPU.

With no GPU or any third party GPU (even a real Mac Edition one), the GPU_OK LED will be off.
 
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tripmusic

macrumors 6502
Original poster
Oct 26, 2012
395
58
Switzerland
To get GPU_OK lit, you need an AppleOEM GPU.

With no GPU or any third party GPU (even a real Mac Edition one), the GPU_OK LED will be off.
Look at the 2nd video I posted about half way through. That's when it stays on with no CPU in the socket. The focus is off, but you can see the two bottom green LEDs on, which are EFI DONE and GPU_OK. I know it seems odd with no GPU installed. Maybe it's just an oddity without the CPU in the socket?
 
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woefi

macrumors member
Oct 17, 2013
30
9
With no GPU or any third party GPU (even a real Mac Edition one), the GPU_OK LED will be off.

Sorry to selflishly plug a question here, but: Whats up, if the GPU OK does _flash_?
(This only happens if I swap my known-good single tray with a dual-tray, and only if I try with two x5690)
 
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tripmusic

macrumors 6502
Original poster
Oct 26, 2012
395
58
Switzerland
I suspect that my problem is the voltage sensor that's just gotten worse and is causing the MP to shutdown/not boot. Sucks because I only picked up this board a few months ago and feel like it was just a waste of money. With all the money I've spent, motherboard/PSU, I could've just bought a whole machine. So I'm leaning towards picking up another motherboard and crossing my fingers. If I encounter any errors running ASD, I'll contact the seller right away.
 
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tsialex

macrumors G3
Jun 13, 2016
8,354
8,867
Sorry to selflishly plug a question here, but: Whats up, if the GPU OK does _flash_?
(This only happens if I swap my known-good single tray with a dual-tray, and only if I try with two x5690)
Several people reported over the years that some early-2009 dual CPU trays are problematic with X5690 and works fine with X5680. I never got one of these trays on hand to investigate why. AFAIK, no one capable of tracking this got one of these problematic trays, so it's a mystery up to now.

Flashing GPU_OK is not on Apple documentation I have, not on ASD or Apple Technician Guide, just checked.
 
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