iMac 20 inch. 2008 not connecting, it stopped working suddenly.

hello, would like a guidance what should I do, my iMac 2008 model A1224 intel 2.4 ghz EMC 2210 not alloy, initially thought to be the source of feeding, as I have 2 equal iMacs, took the power supply from the other yet he does not alloy, reading something here in ifixit, I realized that the LEDs of the logic board are not lighting, which could do to restore it? Any test that I can do (I multimeter).

Thank you.