iMac won’t power up

So what was everything you tried? Also what happened when it stopped working? You need to give us a bit more.

All you've offered us is nothing more that telling the doctor I'm sick, but the doctor needs clues! What is the ailment: you can't eat, you can't sleep, your arm or leg hurts or your head is dizzy?

So what are the symptoms that preceded, what event happen like a lightning storm or power outage?

I'm sorry to hear that your iMac won't power up. There could be several reasons for this issue, and I'll provide you with some troubleshooting steps to help you diagnose and potentially fix the problem:

1. Check the Power Source:
   • Ensure that the power cable is securely connected to both the iMac and a working power outlet or power strip.
   • Try a different power outlet to rule out issues with the outlet or power strip.
2. Reset the SMC (System Management Controller):
   • If your iMac is not responding, resetting the SMC can sometimes resolve power-related issues. The process for resetting the SMC varies depending on your iMac's model. Check Apple's official support website for specific instructions for your model.
3. Check for Physical Damage:
   • Inspect the power cable and power adapter for any visible damage. If you find any, replace them.
4. Test with a Different Power Cable and Adapter:
   • If possible, try using a known-good power cable and adapter to eliminate the possibility of a faulty cable or adapter.
5. Attempt a Safe Boot:
   • Start your iMac in Safe Mode by holding down the Shift key during startup. Safe Mode performs certain checks and may help identify and resolve issues.
6. Disconnect External Devices:
   • Disconnect all external devices (such as external hard drives, printers, etc.) and then try powering on the iMac. Sometimes, a faulty external device can prevent the computer from starting.
7. Check for Display Issues:
   • If the iMac appears to be getting power but there's no display, it could be a problem with the monitor. Try connecting your iMac to an external monitor to see if it displays anything.
8. Perform a PRAM/NVRAM Reset:
   • Resetting the PRAM (Parameter RAM) or NVRAM (Non-Volatile RAM) can sometimes help with power issues. To do this, turn off the iMac, turn it back on, and immediately hold down the Option, Command, P, and R keys. Keep holding these keys until you hear the startup chime a second time.
9. Seek Professional Help:
   • If none of the above steps work, it's possible that there is a hardware issue that requires professional diagnosis and repair. Contact Apple Support or visit an Apple Store or authorized service provider for further assistance.

Remember that working on the internal components of an iMac can be complex and should ideally be done by a qualified technician. If your iMac is still under warranty, it's advisable to contact Apple for assistance.