I have a custom built system that has worked fine for about a year. The other day the system will not power on. When you press the power on button the leds flash for a second and all fans begin to turn but then nothing. No changes had been made to the system hardware. I pulled all the cards checking with each removal and still the same thing. I also tried each of the two memory sticks individually and in different positions, same result again. I pull and reseated the BIOS battery but have not chaecked it for voltage (need to bring a meter home from work). The MB power light is on whenever power is applied. I also disconneded the drives, DVD's, floppy, etc. with the same result. I also pulled the CPU fan and reseated the CPU and fan again still the same problem. I also disconnected the MB power caple and jumpered the Green to Black wires and the power supply started (again I do not have a meter to test the output). Upon reconnecting the MB power cable I had the same problem. All of this was last week and I did not have time to work on the system again until yesterday. I turned the system on yesterday and it started????? I restarted and started the system, powered off and retarted... Everything was fine
Today I am back to where I was before and the system will not power up. I started again as I did above and removed most of the cards. When I disconnected the 4 pin CPU power cable on the MB and the power supply will start and the drives will run up when pressing the power switch. Plug it back in and it will not start.
Any ideas as to where I should start? Power supply, MB, CPU ????