Hello everybody. I need some help, if anybody can answer me. I recently bought a 2009 Mac Pro 4.1, 2,66 ghz single processor. He came with broken PSU, with a pc GPU and no power cord. It was really cheap. I've tested the first time, put a power cord and push the on button. I've heard the classic DING and nothing else. Second time, it didn't work. So, I've acquired from ebay a new PSU, almost identical, the old one was DELTA Part No 614-0435 and the new one is AC BEL Part No 614-0436, same output 980W. I think they are the same: I've put it in, press the on button, nothing happens. I've take it apart, removed everything (HDD, battery, cables, bluetooth) for the minimum configuration test. When the power cable is attached, two red lights (OVTMP CPUA / OVTMP CPU B) are on for almost a second. When i take it off, again, the two red lights. When I press the diag button, the (5V STBY) it turns on. This was the first step according to the service manual. So all good, no? Second step is to reinstall processor cage with fans and processor board. Do not reinstall processor(s), heatsinks, or memory. Did that, 5V STBY turns on. The manual says: Momentarily jump the SYS_PWR solder pads to turn ON the Mac Pro. Well, nothing happens here. Expected behavior: • Front and rear processor cage fans (and PCIe fan, if installed) should spin slowly • One red-colored error LED illuminates on the processor board (next to the memory slots). 7. Press and hold the DIAG button. Expected behavior: • PSU PWROK (green), 5V STBY (amber), EFI DONE (green), GPU OK (green) LEDs illuminated • No startup tone • Front and rear processor cage fans (and PCIe fan, if installed) should spin slowly Nothing on pressing the DIAG button, same yellow light from 5V STBY led. In the manual, is nothing (or I cannot find it) if this step is failed. Anybody have any idea what I should do? Is a failure from the logic board or the new PSU ? Thank you.