Why doesn't my iMac turn on?

Hi,

my 2010 27" iMac fails to turn on. I replaced the power supply thinking that was the problem but it still won't boot. When I plug the power in I see the 1st diagnostic light blink 2 times then it stops and nothing, no fans or anything. I tried a different power outlet, different power lead. I even used a different EMI FILTER.

All I get is 2 blinks of the 1st diagnostic board light.

Can anybody help me?

Thank you