Apple New Mac Pro 2013 (Trashcan) - Wont Start Up

[KYBOSH]

Came home today to find my mac unresponsive to my wake commands (mouse or keyboard touch).
I try to restart the computer but am met with the same unresponsiveness.
I do a reset by pulling the mains, pressing the power button for a few seconds and reinserting the power cord.
Same thing.
The power button LEDs would light up but they would die back down after a few seconds.
No other signs of life, no fan, no apple boot chime, no video output signal to the monitor, nothing.

I started by testing the monitor and cables to verify they were working.
I used another computer do this and both worked properly.
I slid off the cover of the Mac and took a quick look around.
The NVME was still a little warm so I popped it out and tried to start the computer.
My thinking was if the HD had died or shorted then it may prevent the system from even booting.
In the absence of a drive or OS the firmware/EFI would kick in and warn that where was no recognizable file structure to be found.
But I was met with the same blank screen, no fan, no sign of life other than the LEDs lighting up.
The power button LEDs let me know that I was getting some power at least.

After a little scurrying on the web I came across the Mac's official service manual along with a few threads on how you could use the built-in LEDs on the I/O board to troubleshoot some issues.

From the photos attached you can see that my #2 and #5 LEDs are a steady green when the system is OFF but plugged in.
This indicates that the system is getting 11V power (#2) and can go into soft power off (#5).
The manual says the #5 LED should be present in all events as long as the system has power.

Then I powered the system on by pushing the power button then pressing/holding the DIAG button to illuminate the LEDs.
This time I got #2, #3, #5 and #8.

LED #3 shows I have 12V power.
LED #8 shows that the system has reached EFI boot.

What I don't have illuminated are:
LED#4 - Platform Reset Release: This indicates that the system has transitioned to a fully running power state.
LED#6 - S0 Power State: This indicates that the SO (full power) state is available.
LED #7 - S4 Power State: This indicates that the S4 (hibernate) state is available.


I didn't get a chance to check the CMOS battery voltage via a testpoint mentioned in the manual as I was going to take the whole thing apart, dust it and change the battery anyway. A few years ago i upgraded the processor to a 12 core IIRC but I dont recall if I changed the battery (probably not). I have read that a bad battery can cause problems but I doubt very much that this is the case here.

My main suspect is the power supply. Its been 10 years since this unit was manufactured and its always ON design means it was powered on (in some state) for all of that time as long as it was plugged into the wall.

[KYBOSH]

Re: Apple New Mac Pro 2013 (Trashcan) - Wont Start Up

So with the power supply out I want to try to figure out 1) is this really the issue and 2) if so how can I fix it on a component level.

The Apple Part Number is 661-7542 or ADP-450AF or FSD004.

Bcos the LED troubleshooting test showed that 12V was present I'd like to try to test this under load but I dont know much about this power supply (like which leads may need to be jumpered to get it to kick into the ON state).

If the power supply is the issue and I am able to troubleshoot and repair that would be a great victory.

Any suggestions or ideas you guys might have would be greatly appreciated!

[KYBOSH]

Re: Apple New Mac Pro 2013 (Trashcan) - Wont Start Up

Just to be on the safe side i went back and checked and replaced the battery. The original Panasonic BR2032 was still in there and it read 3.16v. I put a replacement Panasonic cr2032 which had 3.23v.
Buttoned everything up except the shell and got...crickets. Nothing had changed.
I checked the voltage at the rails and 2 out of 4 read 12v.

Im not sure if they are all supposed to read 12v tho.

[KYBOSH]

Re: Apple New Mac Pro 2013 (Trashcan) - Wont Start Up

I was fortunate enough to come across a fully functional Mac Pro 2013 today.
When I get it in I will swap parts one at a time to see which component is the culprit.
I'll start with the power supply - I/O board combo.
If it's an easily identifiable short or two I will try to see if I can rectify it.

One thing to note, and the reason why I think my issue is related to the I/O board or power supply is, even though I am getting 12v to some of the rails I am not seeing LEDs on the logic board. There is a DIAG button on it but whether I press it with the power on or off i dont see any lights. This leads me to believe that power is not flowing to it.

I also realized that we had severe weather around here on the day this started. Lightning, heavy rain, tornado warning. Even though I have my system on a 1500VA UPS I can imagine that a small spike may have climbed through one of the various components i have hooked up to the Mac (monitor/NAS/Powered speakers) and may have shorted something on the I/O board. All speculation at this point but I'll have to do more research on how something like this can be prevented in the future.

[KYBOSH]

Re: Apple New Mac Pro 2013 (Trashcan) - Wont Start Up

Well I'm back up and running.
The offending board was the I/O board.

I swapped the power supply - I/O board combo to test and my trashcan started right up. I then swapped I/O boards as I had a feeling it was the most likely suspect and I was right.

So I will look into repairing the I/O board . I came across a YT video of someone doing exactly what I did. And what I hope to do when I have time.

https://youtu.be/g88D5Q5xVXc

For those who are wondering what Troubleshooting LED lights actually look like when things are good please see the attached below.

When the system is plugged in but powered OFF there should only 2 LEDs should be showing (#2 and #5 as shown and described in my previous post).

When the system is powered ON and everything is fine then LEDs #2-8 will be ON and a Steady Green. The first LED (#1) is a red LED and only comes on when there is a problem with the flex cables.

I hope this thread will help someone down the line as these systems get older and things start to fail at an accelerated pace. My hope is people will try to fix their boards (or have it fixed) on a component level.

When I get this I/O board on my bench I will see what I can find and try to report back so the next guy may know what to look for.

[KYBOSH]

Re: Apple New Mac Pro 2013 (Trashcan) - Wont Start Up

I had a few minutes and I decided to check out the I/O board for shorts.
It didn't take me long to find the issue.

Exactly like in the video I linked in my previous post I found the offending component. There was a cluster of coil and capacitors (in yellow) that all rang out as shorted when I probed them in continuity mode. The 58888D Mosfet was the culprit (in red). Just like the example in the video I believe mine was shorted out by a surge that traveled through my TB cable from my NAS drives during the storm.

Fixing this should be a piece of cake. According to the teardown schematics this is a Texas Instrument 58888D mosfet. Unfortunately I am having a hard time finding a replacement. I dont see anything about this mosfet online except for the face that its used on this I/O board.

Once I source a replacement I will install it and it should be good as gold. At least I will have a known good backup.

Im a little concerned about the surge/spike that took it out. All my devices are connect to a UPS with surge protection and pure sine power while battery. I need to figure how to minimize the chance of this happening again.

[tupax]

did you find a replacement for the transistor?

[KYBOSH]

did you find a replacement for the transistor?

I did infact find a direct replacement.
I contacted someone at TI and they went through the schema with me and confirmed that the following is a direct substitute for the transistor on the Mac Pro.

https://www.mouser.com/ProductDetail/595-CSD87350Q5D

Hope this helps!