Was it plugged into a UPS?
Was it unplugged from power?
Have you tried an SMC Reset?
Troubleshooting: My computer won't turn on
If your Macintosh computer won't turn on, here's how to troubleshoot it. Please keep in mind that although your computer may display similar symptoms that prevent it from showing video, this article discusses what to do if the computer won't turn on, meaning that when you press the power button:
- You don't hear a startup chime.
- You don't hear any fan or drive noise.
- The power button or power indicator doesn't light up at all.
If your computer doesn't display any video, it may display one or more of these similar symptoms when you press the power button:
- You may hear a startup chime.
- You may hear fan or drive noise.
- You may see the power button or power indicator light up.
If any of these conditions occurs, see Troubleshooting: My computer has no video instead.
If your computer won't turn on, try each of these steps:
- Make sure that the power cord is plugged into a working wall outlet, and that it's properly connected to the power adapter. (To check if the wall socket is working, plug in a lamp or other electrical device.)
- Make sure that the power adapter is properly connected to the power port on the side or back of the computer.
- Disconnect all accessories that are plugged into the computer, such as a printer, hub, or other mobile device.
- Reset the computer's PMU, SMC, or PRAM. Refer to the instructions for your model:
reset SMC For "Mac wont' turn on or boot" and related
General purpose Mac troubleshooting guide: Isolating issues in Mac OS X
Creating a temporary user to isolate user-specific problems: Isolating an issue by using another user account
Identifying resource hogs and other tips: Using Activity Monitor to read System Memory and determine how much RAM is being used
Starting the computer in "safe mode": Mac OS X: What is Safe Boot, Safe Mode?
To identify potential hardware problems: Apple Hardware Test
General Mac maintenance: Tips to keep your Mac in top form
Morning the hatter
I have tried resetting the SMC and the system has had no change. I have read other posts in the forum and 1 in particular stated they replaced the PSU and now the machine is running fine, boot up and shutdown as normal. I will look into doing this and hopefully this will solve the issue. Thank you for your assistance, if there is anything else that may come to mind please let me know.