Mains power cut to house - iMac now DEAD

Try resetting both the SMC and PRAM and if you get the machine to start back it up today! There is absolutely no excuse for not backing up, none! You can get an external HD connect it and use Time Machine which is the easiest method of backing up. Here are correct instructions for resetting the SMC and PRAM:

SMC RESET

• Shut down the computer.
• Unplug the computer's power cord and all peripherals.
• Press and hold the power button for 5 seconds.
• Release the power button.
• Attach the computers power cable.
• Press the power button to turn on the computer.

PRAM RESET

• Shut down the computer.
• Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
• Turn on the computer.
• Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
• Hold the keys down until the computer restarts and you hear the startup sound for the second time.
• Release the keys.

If the shut down of the power damaged your computer in such a way that it truly won't start up again the harddrive inside can be removed and it is possible that your data (photos, movies, pictures) might still be salvagable by a technician. Sorry to hear about your loss. Good luck with your problem.

A 6 year old computer of any make is on the down hill side of the life expectancy of its parts. The power supply may have been on its last leg and even a proper shut down may have been its last. If you have the funds then a new Mac may be in order and a tech may be able to help you retrieve the data off the old drive. You also need to find the funds for a couple of backup drives!

I figured your were in NZ when you mentioned the "mains" and said that it was already Mother's Day. I have a couple Anglican priest friends on line in Christchurch. 😉

Here is what Apple says to do with an iMac that won't start, it's from the owner's manual.

I don't know which keyboard you use but the command key on my keyboards is the one directly to the left and right of the space bar and is clearly marked "Command."

And may be marked by one of these - ⌘

If you don't hear anything or see any lights at all then it points the finger at a failed power supply. IMHO your next stop is a AASP to see if it's worth being repaired, that will be your call. If it's only the power supply you can salvage the HD and put it into an enclosure. Once you have the HD in an enclosure once you have replaced the iMac with a new machine then you can recover your data. This time BACK UP however at this point I'm sure you know that now.

Hi jacqui, I'm sorry to hear your iMac is not powering on but it is very likely only the power supply is damaged, and that all your photos and other files are perfectly OK. They are just locked away in a computer that won't turn on.

The power supply itself is not terribly expensive to replace (at least in the US). It's less expensive than replacing a hard disk, which as rkaufmann 87 already said can fail at any time for a variety of reasons.

Merely turning off the mains power should not have caused this. I am inclined to believe your power supply was on the verge of failing and this event brought about its demise.

... We have a surge protector which would have been on and working, ... and the surge protector is the same age,

Surge suppressors use components that are life-limited. Their lifespan is limited by the amount of energy they are capable of absorbing. Some have LEDs that indicate whether this protection is still active, some do not.

A surge suppressor that old is probably in need of replacement. It's fine to use as a power strip, but do not rely upon it any longer to protect your iMac from voltage transients. If you live in an area where power quality is not good you should invest in a UPS. They are not much more expensive than a good surge suppressor and are more effective at equipment protection. I use a UPS for every piece of "expensive" electronics I have.