This is my second custom PC that I have built. I have tried everything to try to get it to turn on.
Kingston HyperX Blu 4GB (2 x 2GB) DDR3 1600
DIAMOND A5970PE52G Radeon HD 5970 2GB
AMD Phenom II X6 1100T 3.3GHz
Seagate Barracuda Green ST1500DL003 1.5TB 5900 RPM
ASUS M4A88T-M AM3 AMD 880G AMD Motherboard
The first few times the computer powered up but would not POST, it beeped 1 long 2 short, now it won't even power up. The green LED light on the motherboard is lit. I have tried getting it to power up out of the case and only using the CPU a one stick of RAM. I know the RAM is compatible with my motherboard and the RAM is fully in the slot as well. I have also checked for shorted out cables and I have tried clearing the CMOS. I have tried three different PSUs, all with at least 500w of power. The 4 pin CPU fan power cable is connected and so is the 24 pin motherboard power cord. The 2 pin power cable is connected to the motherboard. I have tried jumping the PSU.
At this moment I suspect it might be the motherboard, but I'm still not sure.
1 long and 2 short is a video system error.
Have you tried with both the onboard and your discrete card? I am assuming you probably have. Although, clearing the CMOS should have defaulted the board to use the onboard video first. Starting to sound to me like you have a bad board as well.