I'm new to MacRumors; this is my first posting. I've read the FAQ but if I'm doing anything wrong, here, please forgive and correct me. Thanks! The other night a power problem in my office took out my Mac Pro; it appears to have been a defective UPS, of all things. The system is: Mac Pro 5,1 (Mid-2010) A1289 (EMC 2314) 3.33GHz HexCore (Westmere) 16GB RAM, 512MB SSD (+3 4TB drives) I came in to find that the Mac Pro, while appearing to run (lights, fans, etc.) had no display output and was unresponsive to system devices (could not eject optical drive trays, for example). Checked and found that the UPS was malfunctioning. I have been following the diagnostic procedures in the Apple service manual (which I found at www.tim.id.au – an invaluable resource, for those working on the systems covered there) and am hoping for confirmation and information from those with more experience. I pursued the following diagnostic path: 1) I connected the system to known-good power; same behavior as above. I put it on the bench, got out the service manual and checked the diagnostic path. When the power button was pressed, the system fans and drives spun up normally. The front panel power LED lit up without flashing. The Processor Error LED on the processor board lit momentarily, as is normal. The display remained dark but gradually became populated with fine, green vertical lines. There was no startup chime nor any sign that input devices had any effect. 2) I performed an SMC reset; I attempted to perform a PRAM reset but, again, no input devices appeared to be effective. I know of no way to reset the PRAM on a system that won’t boot to the grey Apple splash screen, since the Cmd-Opt-P-R key combination does not work short of this stage. 3) Performing the minimal hardware procedure, I found that with the system completely stripped (only the power supply connected to the logic board), when the power cord was connected: • OVTMP CPUA and OVTMP CPUB LEDs light for .5 seconds • 5V STBY LED lights green when the DIAG button is pressed So it appears the system is getting power and that the PSU is at least nominally OK. (these are the expected results) 4) The next step in the minimal hardware procedure is connecting the processor board. Per the procedure, I removed the RAM, the heat sink and the CPU from the board and installed it. The procedure, at this point, specifies that you need to short across the SYS_PWR solder pads to power up the system, at which point the PSU PWROK (green), 5V STBY (amber), EFI DONE (green) and GPU OK (green) LEDs should illuminate and the processor cage fans should spin slowly. 4a) I found, however, that once the board was installed, the instant the power cord was connected, the fans started spinning slowly. Neither the power button nor the front panel board were connected to the logic board, nor was I shorting across the power-on solder-pads to make this happen. All these steps were performed a few days ago; at this point, I had to drop my investigation to attend to other matters. 4b) Then, this morning, I performed the procedure again and found that that the behavior has changed; now when I connect the components as described above, I have to short across the solder pads for the system to power up. In both cases (before and today), when power is connected: • OVTMP CPUA and OVTMP CPUB LEDs light for .5 seconds • 5V STBY LED lights green when the DIAG button is pressed • PSU PWROK (green), 5V STBY (amber), EFI DONE (green), GPU OK (green) LEDs illuminate • Fans spin slowly (these are the expected results) 5) At this point, I connected the front board so I wouldn’t have to short across the pads each time, reinstalled the CPU and its heat sink and 1 DIMM (in Slot 1). The system powered up with: • a brief flash of the processor error LED on the processor board. • a chime 10 seconds after power-up (these are the expected results) 6) Then I connected a hard drive with Mac OS 10.11.6 on it. It is a solid state drive, so I could not hear it spin up. Powered up with: • System chime after 11 seconds • Optical Audio Out port lit up after 27 seconds or so which, the manual indicates, is a sign of driver load. The manual says the port should light “shortly after start”; it lights 27 seconds after pushing the power button and 16 seconds after the system chime. When the DIAG button was pushed: • SYS_PG LED was lit • EFI_DONE LED was lit (these are the expected results) 7) The next step was to connect a graphics card and display. I had feared that my cinema display had been damaged (power-related damage can be widespread) and tried connecting it to a MacBook Pro with a Display Port; it worked perfectly, so I know the display is still good. I have no GPU except the one that was in the system (an ATI Radeon HD 5780/1GB) when the event occurred, so was unable to use the swap-out technique for this step. When I connected the GPU and started up: • nothing on the display • a system chime EVERY 3.5 SECONDS or so – faint but perceptible. Also,when the DIAG button was pressed: • SYS_PG LED was lit • EFI_DONE LED was not lit • GPU OK LED was lit 8) The final step I could perform was to move the GPU to PCI Slot #2 to see if the problem was defective backplane circuitry at PCI Slot #1. The results were exactly the same as shown in Step 7. Interestingly, if the system has been shut down for awhile, the first time or two that it is powered up, there is only one system chime; all other symptoms are as shown. After the first couple of power-ups, though, it starts recursively chiming as described above. My guess is that this is caused by capacitor(s) that are not fully charged the first time or two and discharge after power-down or something of the sort but I may well be wrong here and would be glad of any correction or insight. My questions are these: 1) Can you think of any reason for the behavioral change between Steps 4a and 4b? Is it significant? 2) The GPU appears to clearly be at fault. Should I be worried about the backplane as well? 3) Is there a way to reset PRAM when the system won’t boot to the splash screen? 4) What would be your recommendations for “best” or “close-to-best” graphics cards? 5) Are there any concerns or aspects I’ve overlooked and, if so, what are they? I realize that this has been a long and, perhaps, tedious posting. I want to sincerely thank you for reading and considering it. And thanks in advance for any insight, words of wisdom or corrections you may have to offer. I really appreciate them.