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4,1 Mac Pro, won't power on

G

GT0336

macrumors newbie
Original poster
Jul 5, 2012
9
0
QLD
I have an early 2009 Mac Pro 4,1. The system will not power on at all. When I connect the power cable, I can see a red light through the front vent flash for a second, but when I press the power button, nothing. No sound, fans etc.

I have tried removing GPU, Ram, HDD etc but no change. Is this likely to be a power supply? As the system must be getting some power for the red light to blink. Thanks in advance.
 
Anyone able to offer any advice before I take the plunge and purchase a new PSU?
 
I purchased a new Power Supply today, installed it and still the Mac Pro won't turn on. No fans, nothing. All I get is the red light inside will flash once when the power cable is connected. Any ideas?
 
According to the Apple technician, they said the 3 main suspect (for no power up) are the PSU, mobo, and GPU.

Since you already try the PSU and GPU (by removing it). The biggest suspect now is the mobo.

If you have another friend has the 4,1, may be you can take your CPU tray to there and test it. If all the tray, CPU, RAM works fine. Then the remaining source of trouble will be the mobo and the power socket.
 
Thank you for the info. I'm going to test the front power button ect today. When I press the diag button on the main board the 5V STBY led lights up. The machine has also powered on 3 times after many attempts, but then shuts off again shortly after. Would these symptoms be consistent with a motherboard failure? Thanks again.
 
Hard to say because if you have ANYTHING connected, any memory installed, etc. it could be one of those devices or memory.

You removed everything and tested before replacing the PSU. Have you done that again. We need to isolate the cause down because your situation sounds just like what we went through and a new PSU fixed our problem.

When pressing the power button do you hear anything? Our unit would do a single "click" noise but nothing else would happen. Was able to get the 4,1 to start and when it did I took the opportunity to do a fresh backup and make it ready for service.

If you have removed all items, HD, memory, disconnected all USB devices, removed the GPU and you still cannot power on then it is either the new PSU (it could be bad, would need to bench test it) or the mainboard (logic board, motherboard, etc). From there you would need a known, good PSU in your unit and if it still won't power than the mainboard is the likely suspect.

Good luck. Diagnosing these things takes time and sometimes money.
 
Does this look like the issue either one of you had? I had to push and hold the power button till I heard a click and then it would power on the next try.
 
Yes, seems like what my wife's 2009 went through. It was a power supply (so far). $400 at SimplyMac with bench charge, labor and tax. New Apple PSU was about $220 per the invoice.
 
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