iMac Pro iMac Pro will not start after rebuild

[Regulus67]

I purchased an iMac Pro recently, and the exhaust air was warmer than my other iMac Pro. So I decided to open it up and clean it up, with new cooling paste, while I was at it. In addition, I also installed larger SSDs, going from 2TB to 4TB.

As expected there was some dust, but not to bad.

The CPU is held in place by the cooler only.

Time for new thermal paste

18-core CPU

GPU Pro Vega 64 16GB

New thermal paste

Second hand SSD modules

It is important to install the modules in the correct slot. 01 on the left side, towards the In/out ports at the back.

Everything cleaned up and reinstalled

Having built my own DIY 5k Display from an old 27" late 2015 iMac.
I felt pretty comfortable throughout the whole procedure, going slowly and methodically through the steps.

 

[Regulus67]

Next step is to restore the iMac Pro with the "new" SSD kit installed.
I tried with Apple Configurator on another iMac Pro running Monterey. After several attempts at both restore or revive, I couldn't get it to boot.
Next was pulling everything apart again, to check if I had made some mistake assembling it.

After reassembling it again, I tried again. No luck.

So next option.
I ran Apple Configurator on my Mac mini M1, but didn't seem to have much luck there either.

It has a progress bar going through 4 steps. Last one takes like 5 mins, and says system install, but it only stays at half bar, with no progress. Until it says it not booted. I guess the iMc Pro restarted.

I went through a few attempts again, using either Restore or Revive Device.
But still it will not boot, as the display stays off and the fans doesn't start either.

So I tried a new option with Sonoma or later installed.
Open Finder instead of Apple Configurator. And bring the iMac Pro into DFU mode by pressing the power button while plugging in the power cord.

This is more helpful as you see what is going on and explanation text under the progress bar.

Having gone through all of these steps, and trying to discover how I can get the machine to boot. I am no closer, it seems.
I am fairly certain I have not damaged the display. As I have been very careful opening it, and removing or installing the ribbon cables.

 

[PaulD-UK]

Maybe it's the replacement SSDs that are the problem?
If all else fails try with the original ones...

Is the 18 core CPU a replacement?
If not, maybe that is the source of the extra heat when it was running.

 

[Regulus67]

Maybe it's the replacement SSDs that are the problem?
If all else fails try with the original ones...

Is the 18 core CPU a replacement?
If not, maybe that is the source of the extra heat when it was running.

Yes, the only parts I replaced was the SSDs.
It came with 18-core, 64GB and 2TB.

I will take it apart again, and try with the original 2TB kit. But I am considering one step before that.
I could install the display on my DIY 5k, instead of the late 2015 panel. Just to check if the panel is still functional.

You used a panel from the iMac Pro. So will my ribbon cables fit, except for a slight displacement of course?
But that shouldn't matter as I can leave it partly open while testing.

 

[PaulD-UK]

Yes the R1811 ribbon cables are a direct fit.

Have you got the official "iMac Pro" repair guide, it comes up with Google.

 

[TwoH]

Considering it looks like you’re managing to get the machine into DFU-mode we can at least have some relief that your machine looks like it is still functional (to a degree).

Are you able to identify how many diagnostic lights you are getting on the machine when you plug it in and press the power button?

Swapping to the original SSDs would be a good shout, and depending on your diagnostic LED count, it might be worth giving the RAM a re-seat, perhaps after the repaste and reinserting of RAM, it’s slightly unseated and misbehaving.

 

[Regulus67]

Yes the R1811 ribbon cables are a direct fit.

Have you got the official "iMac Pro" repair guide, it comes up with Google.

I just found the repair guide, thanks for telling me it exists 🥰
And good news that the ribbons fit. That will be easier to test first, than to take everything appart again

 

[PaulD-UK]

According to a quick scan of the Repair Guide the SSD numbers are 00 on the CPU side and 01 on the PSU side.
Is that what you have got?
You're pic looks they're swapped?

 

[Regulus67]

According to a quick scan of the Repair Guide the SSD numbers are 00 on the CPU side and 01 on the PSU side.
Is that what you have got?
You're pic looks they're swapped?

That is interesting. The diagram is indeed swapped.
I installed according to the original SSDs, which I took a photo of, before I started disassembly

 

[PaulD-UK]

The actual pages of the guide, near the end, just says 'replace them the same way round'...
The guide pics are blurred to conceal which way is which.

EDIT: Another page (via Google) confirms you have it right, it seems...

 

[Regulus67]

The actual pages of the guide, near the end, just says 'replace them the same way round'...
The guide pics are blurred to conceal which way is which.

EDIT: Another page (via Google) confirms you have it right, it seems...

I could try to swap position. As your diagram show the other way. And my machine refuses to boot. It is worth a shot 👍

 

[Regulus67]

The Mac Pro 7.1 (2019) has specific slot numbers for the SSDs. And they are marked. The iMac Pro slots are not marked. So there is a chance the kit I got had been installed in the opposite position

 

[Regulus67]

...
Are you able to identify how many diagnostic lights you are getting on the machine when you plug it in and press the power button?

Swapping to the original SSDs would be a good shout, and depending on your diagnostic LED count, it might be worth giving the RAM a re-seat, perhaps after the repaste and reinserting of RAM, it’s slightly unseated and misbehaving.

I can not find any diagnostic lights on the iMac Pro. You sure about that?

 

[TwoH]

I can not find any diagnostic lights on the iMac Pro. You sure about that?

They exist in the circled bit from your original picture. The button just below them must be pressed down to actually have the lights light up

 

[Regulus67]

They exist in the circled bit from your original picture. The button just below them must be pressed down to actually have the lights light up

Oh ok. I guess I could test that without the display panel connected

 

[Regulus67]

EDIT: Another page (via Google) confirms you have it right, it seems...

Yes, it did not work with in the swapped position

 

[tonyelo]

I purchased an iMac Pro recently, and the exhaust air was warmer than my other iMac Pro. So I decided to open it up and clean it up, with new cooling paste, while I was at it. In addition, I also installed larger SSDs, going from 2TB to 4TB.

As expected there was some dust, but not to bad.

View attachment 2482830

View attachment 2482831

View attachment 2482838

The CPU is held in place by the cooler only.

View attachment 2482839



Time for new thermal paste

18-core CPU

View attachment 2482843

GPU Pro Vega 64 16GB
View attachment 2482844

New thermal paste

View attachment 2482846

Second hand SSD modules

View attachment 2482850 View attachment 2482851

It is important to install the modules in the correct slot. 01 on the left side, towards the In/out ports at the back.

Everything cleaned up and reinstalled

View attachment 2482857

Having built my own DIY 5k Display from an old 27" late 2015 iMac.
I felt pretty comfortable throughout the whole procedure, going slowly and methodically through the steps.

Something similar happened to me with an upgraded SSD on a MacBook Pro... There was an issue with the firmware when I tried to install the latest software and updates. I had to purchase and re install an original SSD, then upgrade everything and finally I installed the new SSD and no issues at all. Maybe it works in your case.

 

[Regulus67]

... re install an original SSD, then upgrade everything and finally I installed the new SSD and no issues at all. Maybe it works in your case.

Did it have a T2 chip?
I am asking, because I fail to see how updating macOS on the old SSDs would have anything to do with SSDs that are being installed. As it has to restore the SSD pair and lock it to the T2 chip with Apples configuration tool, in DFU mode

 

[tonyelo]

Did it have a T2 chip?
I am asking, because I fail to see how updating macOS on the old SSDs would have anything to do with SSDs that are being installed. As it has to restore the SSD pair and lock it to the T2 chip with Apples configuration tool, in DFU mode

It was 2015 model so I don’t think so, I think this article describes what happened to me back then… https://discussions.apple.com/thread/253316253

 

[Regulus67]

I put the original SSDs back in. After running Restore in DFU mode, it made no difference. I think it has become bricked.

I also tested the diagnostic LEDs. Pressing down the yellow button, gives one green light LED. Nothing else. Despite pressing power button 10 seconds, and waiting 5 sec to press it once.

The fans give a slight movement after holding the power button for 5 seconds. Then nothing

 

[PaulD-UK]

So, standby power only... 😱
Glancing through the repair guide, the only mention of System shutdown is if the fans are not connected...
Yours turn (well, twitch) so that seems not a problem.

But the 2nd LED should come on if there is the full power available, so it seems the logic board isn't enabling that, or the PSU isn't providing it.

Maybe the fact that your not getting a Error Bong on startup means something major isn't wrong?
In the old days Macs used to make a hideous hi-level sound of breaking glass if they failed POST....
Now they just beep.

I presume you've tried the Reset SMC/NVRAM stuff that the guide mentions that can be done in an unresponsive state...

EDIT: Wild guesses. The points of concern to me seem to be:
The connector back to the PSU from the logic board to the PSU, located to the left of the screen video cable connector.
Or the ribbon cable to the Power Switch button, bottom left above the speaker socket, but that may be OK from what you are able to do?

These are both 'No Power' checkpoints in the guide.
If the PSU is like in the ordinary iMac, it will supply the Standby power as soon as the mains supply is connected, so the first green light would have lit even is either of these has failed.

 

[Regulus67]

So, standby power only... 😱
...
I presume you've tried the Reset SMC/NVRAM stuff that the guide mentions that can be done in an unresponsive state...

EDIT: Wild guesses. The points of concern to me seem to be:
The connector back to the PSU from the logic board to the PSU, located to the left of the screen video cable connector.
Or the ribbon cable to the Power Switch button, bottom left above the speaker socket, but that may be OK from what you are able to do?

These are both 'No Power' checkpoints in the guide.
If the PSU is like in the ordinary iMac, it will supply the Standby power as soon as the mains supply is connected, so the first green light would have lit even is either of these has failed.

I did the reset NVRAM a few times. Holding down power button 10 seconds, wait 5 seconds and power on.

I am going to try to have a technician look at it. There is an Apple Certified dealer in Karlstad, not to far from my place.
They have tools for repairs

 

[Noot]

 

[Noot]

https://www.ifixit.com/Answers/View...do+not+work+in+the+iMac+Pro+2017#answer701001

 

[Regulus67]

Thank you Noot. I had already seen those, when I did a search as well.
The links in the repair manual does not work, that I downloaded as well.
But I suppose the TP1625: How to Use Mac Configuration Utility, refers to the Apple Configurator app