A family friend has an iMac G5 which just totally died, i.e. nothing happens when you press the power button. I followed this apple troubeshooting guide which suggested it to be logic board failure. In some crazy coincidence I had a spare logic board for that computer so swapped it in but it still has the same symptons. This surely suggests power supply rather than logic board. However why does the apple knowledge base article say it is logic board. I tried taking the additional components out to see if it could be another issue e.g. superdrive, harddrive etc but it doesn't do anything even when it is just the logic board and power supply. I am not sure if it is worth repairing this machine I found the part on a website for £180, or one from iFixit for about £130 and some on ebay for about £70. Could it be anything other than the power supply? Is there a way I can test the power supply to confirm before ordering the new part?