MP 1,1-5,1 2009 Mac Pro Random Shut downs

[Ofpaintandpoly]

I’ve been having issues with my 2009 Mac Pro. Where it will shut off randomly, turn back on, shut off, repeat..
I have a 2009 Mac Pro flashed to 5,1 with dual 3.43ghz processors (12 core) 32gb of ram, the original nvidia 512 GPU in slot 3 and an AMD RX580 in slot 1.

Troubleshooting methods I’ve tried:
-The hardware elimination test. Everything checked out okay..
-Repasting and replacing heat sink supports over northbridge diode. It doesn’t seem like an overheating issue. MacFans has insured me that the setup runs fairly cool.
-Voltage tests on PSU.
-Static free deep cleaning, including fans.
-I have replaced the logic board and flashed it myself within the past year, so I don’t expect the problem to be there…
-I have tried multiple GPU’s, processor bays, and Hard Drives with various OS installed… It does not seem like a software issue.

This random shut down, start up, shut down has occurred over the past three years. It will be completely fine for a few months, and then BAM! It shuts off during the simplest of tasks and won’t power back on for a few weeks until I summon the will power to give it another chance.

Honestly, I’m at my wit’s end, I’m confused, and I’m disheartened. Not sure what to do at this point. This computer is very powerful, and I need it for my work in audio production. ?

Any thoughts..?

 

[tsialex]

First thing is to test your PSU with another Mac Pro (early-2009 to mid-2012), test a known working PSU with your Mac Pro. What you wrote is a classic symptom of a PSU with a intermittent defect.

Btw, is pratically useless to check the PSU voltages without load, without a scope to see the signals and without a data logger.

 

[Ofpaintandpoly]

First thing is to test your PSU with another Mac Pro (early-2009 to mid-2012), test a known working PSU with your Mac Pro. What you wrote is a classic symptom of a PSU with a intermittent defect.

Btw, is pratically useless to check the PSU voltages without load, without a scope to see the signals and without a data logger.

I have a friend who has a working 2010 model, so I may try swapping out our PSU’s to see if it makes a difference… This is the second PSU I’ve had for this Mac. Maybe you’re right…

 

[prefuse07]

OP, how old is your BR2032 PRAM battery?

 

[tsialex]

OP, how old is your BR2032 PRAM battery?

PRAM is a PowerMac relic of bygones era. The battery for Intel Macs is just to keep the Real Time Clock and some strictly time related counters like timesinceboot.

No configuration data is kept by the battery or RTC circuit, all settings are stored inside the BootROM SPI flash memory - the NVRAM is a volume inside the BootROM.

Sleep is dependent on the RTC, since a stuck/incorrectly working RTC/timesinceboot causes havoc with the kernel.

 

[Ofpaintandpoly]

UPDATE:
The issue was the PSU. Luckily, I had another one prepped as a backup. Installed it and the symptoms disappeared.
Thanks, Tsialex!

 

[Ofpaintandpoly]

First thing is to test your PSU with another Mac Pro (early-2009 to mid-2012), test a known working PSU with your Mac Pro. What you wrote is a classic symptom of a PSU with a intermittent defect.

Btw, is pratically useless to check the PSU voltages without load, without a scope to see the signals and without a data logger.

PSU was the issue. Thanks so much!