I'm trying to repair a 2006 Mac Pro which I bought cheaply because it wasn't working. It has a pair of 5130 CPUs which appear to be original. When turned on, the sleep LED lights up, and the fans spin silently, but then the CPUB FAIL LED lights up. There is no turn on chime, or any other sound from the speaker. It will sit there like that for as long as I leave it turned on. Everything seems to be pointing toward a bad logic board, but this is my first Mac Pro, so maybe I missed something. When I bought it, it was missing the RAM and video card. I bought a pair of 1GB Samsung 667MHz FB DDR2 DIMMs, and I have them both installed according to Apple's instructions. I flashed an ATI HD3870 with the Mac and PC 3870 firmware, and confirmed that the video card still works in a PC. For troubleshooting, I've tried it both with an without the video card since I don't have a working Mac to test it in. The RAM appears to be detected, or at least it detects if there's no RAM (the sleep LED flashes if I install the RAM in the wrong sockets, or turn it on with no RAM). I assume it should chime and boot without a video card? I've tried it with one CPU in socket A, or socket B, and I've swapped the two between sockets. If I only have CPU A installed, then CPUA FAIL lights up, in all other combinations, CPUB FAIL lights up. I have thoroughly checked the board over for obvious damage. I have also checked the power supply voltages. I had some free time over the holiday, so as a last resort, I un-soldered the firmware chip, and reprogrammed it with the file contained on the emergency firmware recovery CD using an EPROM programmer. I did try the normal emergency recovery procedure first, but the sleep LCD flashed quickly, and the DVD drive didn't open. There was no change, so I flashed the original firmware back since the recovery image is missing the serial number, and possible other things. If anyone want a copy of the extracted firmware for some reason, send me an email. I'm en electrical engineer, so I could do component level repair if I knew where to start. It would be nice if I had some idea of how it failed. Does this logic board have any known weak points such as soldering problems? Apart from some cosmetic damage, it looks like new, so it didn't die of old age. The fans and heat sinks are absolutely spotless. Before I call it a dead logic board, is there anything I'm missing?