MP 6,1 6,1 mac pro hardware problem

[macguru9999]

I have this 6,1 here and its restarting after a couple of minutes. It starts up and a minute or two later the screen either freezes or just goes black and it either shuts down or restarts. You do not get time to run any diagnostics, not even the apple ones. It has firmware 136.0.0.0.0
1. Its not the system OS. Does the same booted off internal catalina or external mojave.
2. Its not the internal SSD, does the same when its removed
3. Probably not the ram, I tried removing half the ram and tried both pairs of sticks in both pairs of slots. same result.
I have reset the PRAM.
Any ideas ??

 

[MisterAndrew]

I suggest checking out some of the troubleshooting steps in the technician manual posted in this thread.

Mac Pro Cylinder led diagnostics

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forums.macrumors.com

The other option is to schedule a Genius Bar appointment at your local Apple Store.