iMac startup problem!

[nigelvugts]

Hello,

I'm having troubles with my 2011 iMac. When I press the power button, I see the loading bar but then the screen shuts down at around 40% of the process bar. I've tried to turn it on with several keyboard combinations, but nothing seems to work. I've had this problem earlier and them I had to buy a new internal hard drive, so I really hope there's a solution.. Also I don't have a backup (stupid i know...) but I don't really have any important files so I don't mind if all my files are gone. I just really want a solution because I've been busy all day to try to get it to work.. Pleaaassseee someone help me out!

 

[DeltaMac]

Can you boot to the recovery system? Press Command-R on restart.
If not, try booting to your Hardware test ( Restart while holding the D - just the D key (for Diagnostics, eh?? )
Try both the standard, and the extended tests.

But, usually when a Mac shuts off during startup, the hard drive is often the culprit.

 

[nigelvugts]

I just tried to restart it with the D key, but that didn't work. Also I've tried recovery mode several times and I did several things but nothing really works. Isn't there a way to just install a clean version of yosemite?

 

[ApfelKuchen]

I just tried to restart it with the D key, but that didn't work. Also I've tried recovery mode several times and I did several things but nothing really works. Isn't there a way to just install a clean version of yosemite?

Diagnostics looks for hardware issues, it won't help much if your problem is in software.

When you were in Recovery, did you run Disk Utility > Verify? If so, what was the result?

To reinstall Yosemite, boot to Recovery and follow https://support.apple.com/en-us/HT201314

 

[nigelvugts]

Diagnostics looks for hardware issues, it won't help much if your problem is in software.

When you were in Recovery, did you run Disk Utility > Verify? If so, what was the result?

To reinstall Yosemite, boot to Recovery and follow https://support.apple.com/en-us/HT201314

I verified via disk utility and it said I had to repair the disk. Then O clicked repair but it couldn't repair the disk...

 

[DeltaMac]

Then, your next step is to backup your important files, then reinstall OS X.
If you have nothing important that you need to save, then that gets you a step closer…

Use the link that ApfelKuchen provided...
Or, I suggest that you do these steps.
Boot to your recovery partition.
Run Disk Utility, and erase your hard drive.
Erasing your hard drive (hopefully) will take care of the issue that is asking to repair your disk.
Quit Disk Utility.
Choose to Reinstall OS X from the Recovery system menu. And - wait…
When that completes (could take an hour or more), you will have a completely fresh OS X install, that will restart, and show you the new user setup.

Oh, if the Erase fails - you will then need to replace your hard drive.

 

[nigelvugts]

Then, your next step is to backup your important files, then reinstall OS X.
If you have nothing important that you need to save, then that gets you a step closer…

Use the link that ApfelKuchen provided...
Or, I suggest that you do these steps.
Boot to your recovery partition.
Run Disk Utility, and erase your hard drive.
Erasing your hard drive (hopefully) will take care of the issue that is asking to repair your disk.
Quit Disk Utility.
Choose to Reinstall OS X from the Recovery system menu. And - wait…
When that completes (could take an hour or more), you will have a completely fresh OS X install, that will restart, and show you the new user setup.

Oh, if the Erase fails - you will then need to replace your hard drive.

How do I make a backup on my external harddisk?

 

[DeltaMac]

You did say this in your first post:

...
I don't have a backup (stupid i know...) but I don't really have any important files so I don't mind if all my files are gone.

Anyway, if you now want to back up your files anyway, you should be able to copy off files using the terminal.
You could also install a boot system on your external drive, then boot to that, and simply copy the files that you want to the external.
I do suspect that your hard drive is gone, and you won't (easily) be able to backup any files - especially if you can't boot to anything else without your Mac shutting off during boot. This is a symptom that I see occasionally from a dying or dead hard drive. You might recover using some good disk repair app like Spinrite, but it will likely be easier to just replace that hard drive, and install the system on a new hard drive. Even better, consider an SSD for that replacement.