Supermicro X7DCL-i-DL0006 System Status LED is yellow

Hi, guys.
I have a server that's using this mother board. It works fine till last month>
Usually if I plug the power cord in it, it would beep and then the LEDs on the power supply would change from yellow to green, the machine then would start booting.
But now, if I plug it into the power supply, the LEDs would stay yellow, the motherboard gives no beep out at all, the LED 4 on the mother board, which is the System Status LED, is yellow. According to the manual, Yellow indicates that the AC power is connected but System is off.
I thought it was the BIOS that's causing the problem, so I cleared the CMOS, checked the Battery votage, replaced the RAM, even replaced the two new power supply and the new HDD sets. Then I went thought everything on the mother board manual try resetting everything to default, but still problem is not fixed.
How come the system is off while the AC power is connected? Even after I clear the CMOS it's still off. I can't reinstall the BIOS as the DVD drive won't work, any one has any suggestions? Please help, thanks everyone!

 

For anyone that might be in the same problem, do not try to fix the MB as it's faulty, I thought it was the RAM causing the problem but it's not. Had to replace the MB, cheers.