Chosen Solution

Good morning to everyone! I’ve a lot of problem with my old iMac. I’ve changed the CPU (with a Penryn unit) and I’ve worked with it for some months now with no problems. A few days ago, the iMac doesn’t want to turn on, and nothing happens when I push the power button, no fan, no display… Nothing. I thought the PSU was bad, and I’ve changed the PSU out, but nothing happens…. Any ideas or checks that I can do? Do you think that if the CPU was broken the iMac wouldn’t start at all? Thank you for the support! Update (02/02/2018) I’ve done some test: Removed the mainboard: on both sides there are no evidence of damageI’ve changed 2 different CPU’sI’ve removed hdd, dvd, bluetooth, wifiI’ve changed 2 different PSUEvery test without display connected Every time the same results. When I plug the power cord the first LED will start, pushing the power on button the first 3 LEDs will blink, and they shutdown.

Anyone can see the video? Update (02/03/2018) I’ve tried to change:

  • cpu
  • mainboard but always the same results on 2 different mainboard with 2 different cpu :( :( it seems that the psu is the cause again…or there are other options :( :( :( thank you for your suggestion Update (02/06/2018) I’ve opened the imac, I see the 1st led turned on. when I push the power on, the first 3 led blink for just some millisecond, and after, every led shout down. only if i remove the power chord for some minutes the first led will turn on. any suggestion?

Hello Everyone. Just to update my progress, I have successfully restored my iMac A1224 by swapping my GPU card with a good known working one. The iMac is running flawlessly. Thanks.

What does the onboard diagnostic LED’s tell you?

Reading from Left to Right: LED #1 - Indicates that the trickle voltage from the power supply has been detected by the main logic board. This LED will remain ON whenever the iMac is connected to a working AC power source. The LED will remain on even when the computer has been shut down or put to sleep. The LED will turn on only if the AC power source is disconnected or the power supply is faulty.LED #2 - Indicates that the main logic board has detected proper power from the power supply when the computer is turned on. This LED will be ON when the computer is turned on and the power supply is working correctly.LED #3 - Indicates that the computer and the video card are communicating. This LED will be ON when the computer is communicating properly with the video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the video card might be installed incorrectly or need replacement.LED #4 - Indicates that the computer and the LCD display panel are communicating. This LED will be ON when the computer is turned on and video signal is being generated. If the LED is ON and there is no image on the LCD display panel, the LCD display panel or inverter might be installed incorrectly or need replacement. Update (02/06/2018) Well the first LED is telling us the PSU is bad. You’ll need to get another unit to test things. Make sure you get the correct one Apple P/N 661-4433, 170w power supply. I would recommend you disconnect the peripheral devices before powering up in case you have a short somewhere. Also check your wall outlet making sure its properly wired and check the breaker/fuse panel as well making sure its grounded. Often someone who is burning power supplies has bad power! You might invest in a UPS to help protect your system and peripherals.