MP 1,1-5,1 cMP 4,1 > 5,1 dead!?

[DeppJones]

My cMP 4,1 flashed to 5,1 "died" one week ago after a strange behavior.

I have used the Mac for several hours with easy tasks (installed the update of Safari 15.1 during that time) and switched it off afterwards. After a few minutes it started by itself and showed the "Stop"-icon on the screen. I switched it off by pressing the power button. After some time, it started again by itself but this time it booted into MacOS. I shut it down with the shutdown-function.

A few hours later, I wanted to restart the Mac but nothing happened when pressing the power button. Suddenly, it started again by itself with all fans running full speed. Booted into MacOS but I have noticed that "Macs Fan Control" didn't show any temperature values. After approx. 1 minute a small window appeared which I have never seen before. As far as I remember, there were four different options like shutdown, reboot and two others. I have selected shutdown.

After the Mac was shut down, I tried to start it again. The only thing that happened is, the two LEDs for OVTMP CPU A and B are now glowing constanly as soon as the AC cable is connected. The orange/yellow 5V LED is glowing when pushing the test button.

I have completely disassembled the Mac and tried to power on by short-cutting the two solder pads on the back plane. Nothing happened. Since nothing else but the back plane and the power supply are present, in my opinion one of the two or maybe both parts are broken.

When testing the power supply, it makes the click-sound when switching it on and it even delivers 12V with high amperes. The only strange thing I have noticed is a noise from the power supply. But maybe it's because some kind of signal or load on a specific line is missing.

Is it possible that the SMC is broken because I couldn't read any temperatures in Macs Fan Control when it was running the last time. Can I re-flash the SMC?

 

[Macschrauber]

Smc cant be reflashed.

Check the rtc Battery, a CR2032 for a temporary replacement would fit.

Check the Northbridge Rivits, they break and the nb overheats.

Without replacement parts, or better a whole known working Mac Pro it is almost not doable to check the backplane and the cpu board.

5.1 parts fit almost for diagnose. There is a smc mismatch, fans go to full but it helps to sort out things.

 

[DeppJones]

Smc cant be reflashed.

Check the rtc Battery, a CR2032 for a temporary replacement would fit.

Check the Northbridge Rivits, they break and the nb overheats.

Without replacement parts, or better a whole known working Mac Pro it is almost not doable to check the backplane and the cpu board.

5.1 parts fit almost for diagnose. There is a smc mismatch, fans go to full but it helps to sort out things.

The battery has 3,1V and seems to be ok.

Northbridge cooler is as well ok.

What I don‘t understand is the fact, that even with nothing connected, the OVTMP LEDs glows. How can the backplane detect an overheated CPU when no CPU tray is connected?

 

[Macschrauber]

afair OTMP Led lit is is not normal behaviour. They are just active very shortly when the PSU is powered by mains.

Without the CPU Board the Backplane does not start the PSU.

How much is the voltage when you measure the two solder pads for jumpstart the Board without front panel board?

 

[DeppJones]

afair OTMP Led lit is is not normal behaviour. They are just active very shortly when the PSU is powered by mains.

Without the CPU Board the Backplane does not start the PSU.

How much is the voltage when you measure the two solder pads for jumpstart the Board without front panel board?

With power supply, back plane and CPU tray connected nothing happens when short cutting the two solder pads.

i will measure the voltage between the „power on“ solder pads tomorrow.

 

[DeppJones]

Replacement back plane arrived today.

Made a quick connection of CPU tray, back plane and power supply. OVTMP only flash once after connecting the AC cable.

Looks like the original back plane died. Is there a common issue that I could check?

 

[14dcutaneo]

Replacement back plane arrived today.

Made a quick connection of CPU tray, back plane and power supply. OVTMP only flash once after connecting the AC cable.

Looks like the original back plane died. Is there a common issue that I could check?

Yes. It’s very likely the flash memory chip U8700 has written itself to death. @tsialex has a really good write up on what to do to if this is the case and what your options are if you want to fix it. Scroll down to “What to do if during the upgrade process your Mac Pro bricked”

MP5,1: What you have to do to upgrade to Mojave (BootROM upgrade instructions thread)

Please fully read this first post, you will probably find that you have one or more problems described into the various notes below. Mojave will only install if you have upgraded your BootROM to the current release and your Mac Pro have a Metal capable GPU*. If you are trying to install Mojave...

forums.macrumors.com