early 2008 imac hot with black screen will not boot.

Question

early 2008 imac hot with black screen will not boot.

I have a 24" aluminium iMac early 2008. The screen went black and it would not boot up although it sounded normal on start up. I had a bootable external backup disk which seemed to work, but after a while-- an hour or so that went down too. It would spin up but then beeped and clicked.. I didn't relate this to the same problem. Then I had the machine repaired with a new ssd. It had an ssd originally. I was happy and it worked for a few days... week. Then that went down again. I see from reading this forum that it seems to be related to heat, fan control etc. Has anyone else had this problem? Do you think the second drive is fried too. Should I just cut my substancial losses and junk this machine. Thanks Tom Piper

Mac Pro, OS X Mavericks (10.9.5)

Posted on Jul 4, 2015 4:10 AM

Reply

Answer 1

Jul 4, 2015 4:51 AM in response to tomfromcardiff

I have this exact same problem which started as soon as I completed the upgrade to 10.10.4. I'm going to attempt to remove the logic board and reapply fresh thermal paste to the CPU & GPU. I hope that will fix the problem. I find if i don't switch the iMac off or put it to sleep, it will work for hours at a time. Once switched off, the screen remains black until the machine has cooled down.

Reply

Answer 2

Jul 17, 2015 1:30 AM in response to Craig_Wright

Fixed the problem by baking the graphics card twice for 10 mins at 200ºC. No more blank screen but another problem has developed the CPU fan runs at full blast. I'm using a fan control app until i can find a fix that problem, I suspect its a failed sensor wire.

Reply

Answer 3

D.Cohen

Level 6

8,588 points

Jul 17, 2015 2:53 AM in response to tomfromcardiff

Try Safe Boot:

- Shut down your Mac

- Wait until your computer turns off and after that press the Power button

- Right after you hear the startup tone, press and hold the Shift key

- Release the Shift key when you see a grey Apple sign and the progress bar below this sign

- After your Mac boots up, restart it as you usually do.

If this doesn't help, follow the instructions below:

- Shut down your Mac

- Wait until your computer turns off and after that press the Power button

- Right after you hear the startup tone, press and hold the Shift key

- Release the Shift key when you see a grey Apple sign and the progress bar below this sign

- Once you see Desktop, start a Disk Utility scan to detect and repair file system errors (don't forget to choose your main hard drive)

- Click on Verify Disk and then, if asked to fix problems, on Repair Disk

- After this, click on Verify Disk Permissions and then on Repair Disk Permissions

- After the process is finished, shut down your Mac and turn it back on after about 30 seconds

Apart from that, take a look at this Apple article and follow the instructions on Resetting NVRAM shown there: How to Reset NVRAM on your Mac - Apple Support

Try resetting the System Management Controller: https://support.apple.com/en-us/HT201295

Hope this helps!

Reply