MP 1,1-5,1 Mac Pro 5,1 power issue

[NickArchiver52]

Hello, I have recently received a Mac Pro 5,1 2.4gb 8-core model, and upon testing, it sometimes starts up, then shut off after 10-20 minutes. Most of the time however it doesn't power up at all. When plugging it in a red LED at front lights for a second and pressing the diagnostic button lights up the "Standby" amber light. I have tried replacing the power supply, swapping GPUs, SMC reset, etc. and it still does the same thing. What's going on here?

 

[tsialex]

Hello, I have recently received a Mac Pro 5,1 2.4gb 8-core model, and upon testing, it sometimes starts up, then shut off after 10-20 minutes.

The behaviour you described is usually caused by a common CPU tray problem. Did you inspected the CPU tray northbridge heatsink push-pins?

clip (snap rivet) for Northbridge heat-sink on 2009 Mac Pro 2X2.26

Just my 46 cents, here. I have just finished completely refurbishing 2 Mac Pro (5,1 - 2010-2012) CPU trays (and am about to do a third) and have had to deal with this problem. In both cases, the original plastic rivets and springs were intact but, after reading numerous reports of failure over...

forums.macrumors.com

Most of the time however it doesn't power up at all. When plugging it in a red LED at front lights for a second and pressing the diagnostic button lights up the "Standby" amber light.

Normal behaviour for the LEDs. CPU tray red LED always lit for second when powering up.

I have tried replacing the power supply, swapping GPUs, SMC reset, etc. and it still does the same thing. What's going on here?

Your best bet is to test the CPU tray with a known working Mac Pro, test the known working Mac Pro CPU tray with yours.