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MP 1,1-5,1 Mac Pro 3,1 no longer starts up


macrumors regular
Original poster
Jun 30, 2007
Looking for any advice on what could be wrong with my Mac Pro 3,1 which no longer boots. I had the machine plugged into a UPS, but the batteries in it are no longer viable. There was a power fluctuation; I heard the UPS beep and the Mac Pro shut down. I have not been able to revive it since.
  • Pushing the power button I can hear and see fans start up, the white power light is solid. I can turn it off with no issue by holding the power button.
  • There is no startup sound or video output to the monitor
  • USB Keyboard appears unresponsive (caps lock light does not activate). However checking with other accessories, USB ports do provide power.
  • RAM risers boards light up red LEDs briefly when I turn it on, and then go out after a second or two.
  • I have removed all non-essential components including all RAM except 2 DIMMS one in each riser, Removed USB3 PCIe card, Removed all SATA drives, Disconnected DVD drive. Left in ATI 5770 and AHCI PCIe SSD (boot drive).
  • I replaced the PRAM battery and cleaned out dust from the inside.
  • Attempted to boot with the original video card it came with (Fan sounded terrible, but other than that it made no difference)
At this point I am thinking either power supply or logic board, but I am not sure which is more likely.
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