prodigy83
Member
I have a Mac Pro A1186 with the logic board 820-1976-A in it. The computer turns on, but it never chimes, it doesn't display any video, the white light on the power button stays sold white, all the fans spin normal. The computer just simply does not seem to post.
Here a some of the things I have already tried:
1.) Replaced PSU with a known good working PSU, no change.
2.) Tested the GPU in another computer, and the GPU works fine.
3.) Removed the RAM trays and cleaned, all seem to be working.
4.) Each time I have reset the SMC and pressed the system rest button in the top right corner. The SMC does reset. The system reset button I believe is doing something because I can hear the superdrive reset each time I press this button.
5.) The Diagnostic LED when the computer is on, the Power on light is green, and the Trickle LED is yellow. When the computer is off, only the Trickle light turns yellow.
6.) I removed the CMOS battery and tried all of these steps with the battery out, but the battery was too low, so I replaced it with a new one and tried all of these steps again.
7.) RAM I swapped in different RAM slots. The computer does recognize when the RAM is not in any of the DIMM slots, and when the RAM (tray board) is also not in the slot, the computer recognizes this too by the white light blinking on the front of the computer.
8.) Thermal imaging camera shows that both processors in the motherboard are indeed heating up, so the processors look good.
Having tested all these things, I am very confident that the problem is with the motherboard, but where would a problem like this be at? All the cylinder capacitors look good. The computer was full of layers of dust, so I am sure whatever happened to it may have been heat related. I cannot find any schematics or boardview files, nor does my subscription I have for the schematics and boardview files have any Mac Pro files.
Thanks for any help in advance.
Here a some of the things I have already tried:
1.) Replaced PSU with a known good working PSU, no change.
2.) Tested the GPU in another computer, and the GPU works fine.
3.) Removed the RAM trays and cleaned, all seem to be working.
4.) Each time I have reset the SMC and pressed the system rest button in the top right corner. The SMC does reset. The system reset button I believe is doing something because I can hear the superdrive reset each time I press this button.
5.) The Diagnostic LED when the computer is on, the Power on light is green, and the Trickle LED is yellow. When the computer is off, only the Trickle light turns yellow.
6.) I removed the CMOS battery and tried all of these steps with the battery out, but the battery was too low, so I replaced it with a new one and tried all of these steps again.
7.) RAM I swapped in different RAM slots. The computer does recognize when the RAM is not in any of the DIMM slots, and when the RAM (tray board) is also not in the slot, the computer recognizes this too by the white light blinking on the front of the computer.
8.) Thermal imaging camera shows that both processors in the motherboard are indeed heating up, so the processors look good.
Having tested all these things, I am very confident that the problem is with the motherboard, but where would a problem like this be at? All the cylinder capacitors look good. The computer was full of layers of dust, so I am sure whatever happened to it may have been heat related. I cannot find any schematics or boardview files, nor does my subscription I have for the schematics and boardview files have any Mac Pro files.
Thanks for any help in advance.
