Long ago, I was given to understand that, when ordering a backplane, it is important to make sure that the product numbers on the replacement board match those of the original. I have a rather different question perhaps you or someone can guide me here. I dismantled the processor board per the Minimum Configuration Test's directions but will reassemble it, test and report back today. Thanks for the swift reply, tsialex! I will check that out poste-haste. Whatever your answers, my sincere thanks and appreciation of the time and energy you spent reading and considering this problem.
I hate to add a processor board to the growing list of replaced components if that is not the problem. One that I didn't need, if that is not the problem, since the original one acted the very same way.Īny insight or advice would be gratefully accepted and carefully considered. At the same time, two backplanes in a row have manifested this behaviour one of them a tested, warranted component. I have swapped out the power supply and the GPU for known good ones.Īt first blush, the processor board looks to be the problem but if the backplane is not supposed to power up the processor board until SYS_PWR is activated (but is doing so), that may indicate some obscure backplane issue not mentioned in the documentation.
I have actually ordered and installed a replacement backplane (tested and warranted to be working by a reputable vendor that I've used many times and having been careful to obtain the exact same model backplane) only to have it behave the exact same way. It is as if the backplane is sending power to the processor board without the essential step of jumping the SYS_PWR pads (and is also illuminating both RAM LEDs). All appropriate LEDs (as described above) illuminate as they shouldĪgain, this happens without jumping the SYS_PWR solder pads on the backplane. At 9 seconds, the processor cage fans begin turning slowly At 4 seconds, BOTH RAM error LEDs on the processor board illuminate In my case, when power is applied WITHOUT jumping the SYS_PWR solder pads, the system behaves as expected but only for 4 seconds. One RAM LED on the processor board should illuminate The processor cage fans should start turning slowly Then the processor board is supposed to be activated by having the technician jump the SYS_PWR solder pads on the backplane, at which point: Initially, it is supposed to behave as shown above. Upon removing power, both CPU LED's flash momentarily (as they are supposed to)Ģ) When the processor board (stripped of CPUs, heat sinks and RAM) is subsequently installed, the system does NOT function as expected. 5V STBY illuminates upon pressing the DIAG button
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I performed the Minimum Configuration Tests as specified in the Apple Mac Pro Mid 20 Technician Guide Service Manual, pages 33-37, and found the following:ġ) The backplane (when installed by itself) seems to test OK with the backplane-only installed and power applied:
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