MP 1,1-5,1 MacPro 5,1 2010 intermitent boot

[Spaceworthy]

MacPro 5,1 2010. seems to be an intermittent fault, it sometimes boots and mainly when cold, on restart it only sometimes reboots. The front light does come on along with all the fans including GPU fan and the 5v amber led works & the PSU green lights up as well, but just sits waiting to boot.
Have tried all the SMC's and other acronyms, still only boots sometimes, and now doesn't at all.

Tried holding the button in for firmware boot and has worked a few times but can not repeat it now.
I have a few other backplane boards and PWR supplies and CPU trays, the other boards light up and then immediately shuts down.
I've tried swapping PWR but the same result, Any ideas on testing and repairing the Backplane board?

 

[expede]

Hi there!
First thing I would do is to "strip down" your cMP to minimum hardware. Try to start with as low hardware as possible. This mean one HD in bay 1 with Mojave system. 2 slots of RAM. One GPU and nothing else. Change the battery. Be sure that the backpanel and the CPU-tray stays the same. Do a 3xNVRAM reset (alt+cmd+P+R) Just the basic. Then I would work my way up.

/Doc

 

[tsialex]

The first thing to do is confirm that the backplane is really the issue and not something simpler like a dead SPI flash or a corrupt BootROM. You can do that with a MATT card or replacing the SPI flash memory with a brand new MX25L3206E flashed with MP51.fd.

After you eliminated the BootROM, replace the backplane with a known working backplane and confirm that the backplane is really the issue. You really need to do that, you have to confirm that everything else inside the case is in perfect shape, don't let something simple that you overlooked make you spent days of diagnostics chasing something that is not really there. Defective SATA disks frequently cause the issues that you wrote.

If you are capable to repair it, start with a visual inspection of the main CIs, see if any has bulges. If any of the main chipset is damaged, junk the board since it's not economical to repair a backplane that you can buy for as little as US$45 with some searching on eBay and just the southbridge will cost you more than that.

If you find nothing with the visual inspection, do your homework:

• start checking the resetable fuses,
• measure the ESR and capacitance of the capacitors,
• look at enable and output of each one of the power controllers with a scope and check all the resistors nearby - sometimes is just a resistor,
• and etc.

Btw, being really honest, anything besides the SPI flash memory is not worth your time since the cost of supplies, parts and etc will be more expensive than a used replacement backplane. Even if you have loads of junked boards to part it, your time is more valuable. While this will change in the future, right now is the best/cheapest time ever to buy any replacement part from eBay.