@tsialex Thanks for the knowledge. I am a newbie when it comes to flashing Mac Pro's using CH341a. Should I mod the ch341a to use 3.3v at the data pin for the flash?
Did you first checked the SPI with your scope? The SPI signals are even showing anything? If is not, then is useless to replace the SPI flash memory.
Currently, it is dumping 5v on the data line. But I believe the MX25L3205D's data pin operates at 3.3V. Isn't it? I have a ch341a that do not have a voltage selector on it. I believe it is one of the old models.
No need to mod the ch341a to flash a brand new MXIC 25L3206E. Btw, even if you mod it, the CH341a is not really safe for non-5V tolerant SPI flash memories.
By the way, here are some more details about the Mac Pro, if it helps. Have you or anyone else in the forum have come across a similar issue?
EMC : 2629
MAC PRO 2.4_12CX/6X2GB/1TB/5770/SD-USA.
According to the serial check at Apple's website, it is a mid-2012 model.
Regards
Yes, but could be anything. If you get 10 Mac Pros to repair, about 7 will have different defects after the 11 to 15 years of usage and usually is more than just one thing to make a Mac Pro to be dead to the point of not giving any clue with DIAG LEDs.
Could be the CPU tray (test with a working Mac Pro), could be a SATA device that is defective and blocking POST (remove/disconnect all SATA devices), could be the backplane, could be the PSU (yes, even if you tested it on the bench and found that the voltages are good, confirm that the PSU is really working with a known working Mac Pro) - could be literally anything. Read previous diagnostics threads.
The thought of flashing the mobo is due to a problem that I have been having with it. It used to boot up and run fine. But recently the mobo started to show problems where it boots with no display but chimes. So I re-balled the video card processor and everything was fine. As this belonged to a customer, he came and picked it up. After a few days, he bought it in again complaining that it would not turn on when the power button is pressed. The OVTMP light flashes when the power cord is plugged and the standby amber led also lights up when the diag button is pressed. I have checked the PSU and it checked out fine.
Test the PSU with a working Mac Pro, checking lines is frequently misleading and no garantee that the PSU is really working.
But there is no activity happening in the cpu tray which is expected. I have tried using the service manual. According to the manual, the backplane may be faulty. As I do not have the schematics, I just wanted to give it a try flashing the SPI and see if it change anything at all.
Apple Technician Manual minimal config is designed for Apple or AASPs technicians with access to Apple own internal diagnostic interfaces (LITTLEFRANK and etc). Not really useful for anyone else.
Get another Mac Pro and test each part one at a time doing the elimination game, is the only way to really do diagnostics in an efficient manner with a so complex system like a Mac Pro without access to Apple diagnostic interfaces.
If you can't do that, your last resort is to test the backplane with a known working PSU/CPU tray with a MATT card or a brand new MXIC 25L3206E flashed with MP51.fd - do not erase the factory one - but only if you verified that the SPI signals are present.
You probably already spent more man hours than the price of a bare bones mid-2010.