A friend gave me an iMac 17" (Late 2006 CD) EMC: 2114 and it can't start. I connected the power adapter and something sounds inside (like a clicking sound), then I pressed the power button and nothing happened. I opened it to check the diagnostics LEDs (It have 3 LEDs). When I connect the power adapter the #1 LED was on, when I pressed the power button the #2 LED turned on, but the #3 LED just blinked once. Up to here, nothing seemed to be turned on. Then I kept pressing the power button (force shut down) and the #2 LED turned off.

I tried once again. I quitted the power adapter, waited 15 seconds and then reconnected it while pressing the power button and the same clicking sound appeared. The #1 LED turned on. I pressed the power button and the LEDs did the same (#2 was on and #3 just blinked once), and this time the fans turned on, but neither the HDD nor the CD nor the screen seemed to be turned on. Neither sound was heard.

Someone told me is both the power supply and the logic board which are the ones to be replace. I quit the power supply and it looks good, the computer doesn't smell burnt. What do you think?