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Question: Power Supply Failure? Or Motherboard?

This morning I started to get a lot of problems with my Early Mac Pro 2008 (3,1). USB Ports and USB 3 PCI card stopped working, so I was forced to manually power down with the power button (long hold). Trying to power back up, when I press the button the fans are at jet engine speed for about 3-5 seconds, then the Mac then shuts itself off.


My reason to question whether this is the power supply or the motherboard is two things: 1) the failure of all USB ports & the PCI extension card (a USB 3 card - thought the SATA card I have in there and the built-in FW400 port seemed to working ok at the time the other ports were failing - I had drive plugged into both the SATA card & the FW400 port), and 2) the Mac did attempt to power on when I pressed the power button (if it were the power supply, wouldn't it simply fail to show the Mac any power at all?).


Before I buy a new power supply, I'm looking for experienced opinions about this. Questions? Ask away, please. Thank you!


--Dave

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If the fans spin up at all, you do not have a power supply problem.


my Mac is mysteriously fine & dandy after a day of being unplugged. This is entirely weird.

The procedure for doing an SMC Reset on these Macs completely removes all AC power, which eventually allows the DC power to drop to zero. When it Starts up again, all chips will been reset, especially the System Management Controller (SMC), which controls clocks, fans, and low speed peripheral devices. This also forces the SMC to re-derive what devices are present.


You did an SMC Reset, a common solution for peripherals disappearing, devices not recognized, or fans out of control.

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Mar 13, 2018 10:49 AM in response to Eau Rouge In response to Eau Rouge

Thanks, Eau! Sometimes I forget about the Safe Mode method of troubleshooting.


If you missed it, I'd posted that my Mac is mysteriously fine & dandy after a day of being unplugged. This is entirely weird. I've never experienced anything like this in 35 years of using Macs. I think the Safe Mode method would be the first thing to do, though, if my Mac freaks out again.

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Mar 9, 2018 7:46 PM in response to kahjot In response to kahjot

So strange. I came back home this evening after leaving the computer unplugged all day, and now the Mac boots like nothing was wrong. I haven't tested all ports yet, but I did have a mouse and computer available, so I zapped PRAM while I had the opportunity. I'll have to do more testing another day.


I don't get it.

Mar 9, 2018 7:46 PM

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Mar 9, 2018 7:59 PM in response to kahjot In response to kahjot

USB2: A keyboard, a Wacom Bamboo tablet, a Logitech gaming mouse, an iPhone cord without an iPhone on the other end. Nothing that I don't usually have plugged in.


USB 3 PCI card, three cables that didn't have drives on the other end and one Sonnettech Fusion QR 4-bay JBOD chassis with 4 drives in it (this is always plugged in, so nothing new there either).

Oh, yes, the other thing tho is that this whole avalanche of trouble started with that Fusion not mounting on the USB 3 card. Drives were spinning but they weren't mounting. When I power cycled the Fusion, it acted like it was having a malfunction by acting like it was going to bring the drives up to mount but just before it got to that point, the chassis would power down. I've had that unit for 2 years and it has a one year warranty, so I figured it's time was up. I unplugged the USB to see if it would power and spin the drives up fully, and it would still start the spin the shut down (meaning the drives would lose power and the fan would stop spinning).

Mar 9, 2018 7:59 PM

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Mar 9, 2018 9:52 PM in response to MyKidsDad In response to MyKidsDad

Try Safe mode, Use safe mode to isolate issues with your Mac - Apple Support then restart as normal.

If you experience the same problem then go through a process of elimination, unplug all peripherals and restart.

Then add one and restart, add another, restart, etcetera until you find which one is causing the problem.

Mar 9, 2018 9:52 PM

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Mar 13, 2018 10:49 AM in response to Eau Rouge In response to Eau Rouge

Thanks, Eau! Sometimes I forget about the Safe Mode method of troubleshooting.


If you missed it, I'd posted that my Mac is mysteriously fine & dandy after a day of being unplugged. This is entirely weird. I've never experienced anything like this in 35 years of using Macs. I think the Safe Mode method would be the first thing to do, though, if my Mac freaks out again.

Mar 13, 2018 10:49 AM

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Mar 13, 2018 10:49 AM in response to MyKidsDad In response to MyKidsDad

If the fans spin up at all, you do not have a power supply problem.


my Mac is mysteriously fine & dandy after a day of being unplugged. This is entirely weird.

The procedure for doing an SMC Reset on these Macs completely removes all AC power, which eventually allows the DC power to drop to zero. When it Starts up again, all chips will been reset, especially the System Management Controller (SMC), which controls clocks, fans, and low speed peripheral devices. This also forces the SMC to re-derive what devices are present.


You did an SMC Reset, a common solution for peripherals disappearing, devices not recognized, or fans out of control.

Mar 13, 2018 10:49 AM

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Mar 13, 2018 10:53 AM in response to Grant Bennet-Alder In response to Grant Bennet-Alder

Thanks!! Would the SMC becoming problematic also stop the USB2 ports and the USB3 PCI card from functioning but leave the FW400 & the SATA PCI card working? I was never quite clear on how the SMC operates and what it can and can't do.

Mar 13, 2018 10:53 AM

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Mar 13, 2018 11:49 AM in response to MyKidsDad In response to MyKidsDad

Death of the System Management Controller (SMC) is extremely rare, but would mean your Mac would not run at all.


What happens is that the SMC gets confused about what Hardware is still connected and working properly. (Its software gets into an odd state.) Doing an SMC Reset sets it right again, at least for a while.

Mar 13, 2018 11:49 AM

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Question: Power Supply Failure? Or Motherboard?