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Resolved iMac 2008, running out of ideas

F

Faloude

macrumors regular
Original poster
Oct 6, 2018
102
17
I have a beautiful iMac 2008 20" (A1224) that so far took 14 hours (and counting) of work. I've repaired over 100 Apple devices and honestly I've never been more puzzled.

Apple iMac "Core 2 Duo" 2.66 20-Inch (Early 2008)

Problem
iMac boots to load screen. At around 80% the screen turns white. It seems the iMac is actually in the login screen because screen dims after inactivity, wakes at button press and prompt sound is heard when pressing power button.

Hypotheses
1) HDD is failing
Took out HDD, connected to USB on my MBPro Retina, diagnosed it, results: failing. Well this is going to be easy! Cloned failing HDD to SSD and mounted in iMac, bam, exact same problem.

2) Well obviously the OS is corrupted so you shouldn't clone from a failing HD.
Used the SSD as a boot drive from 2 different devices and it works fine, so OS is not corrupted.

3) Maybe the OS seems it's not corrupted, but it is! Try a clean 10.11 (el capitan) install.
Created 10.11 (el capitan) USB installer using Install Disk Creator and el capitan downloaded from Apple website. Plugged into iMac, held ALT button, ignores it, no boot menu. Maybe the installer USB is invalid? Tried on MB Retina and MB 2011, works so installer is fine.

4) Many sources say with these older devices you start at 11.5 and gradually upgrade to 10.11. You can't install 10.11 from scratch.
Installed OS X Leopard (10.5). This works. Up next: Snow leopard (10.6). Can't install it, iMac doesnt show boot menu with usb installer plugged in. Try booting to it from within Leopard? It shows the installer disk (10.6) but when selected and clicked "restart" it just makes an error sound without any info

5) Maybe you should try 10.6 DVD
Tried it, same result. Doesn't show in boot menu and "choose startup disk" from settings won't boot from it.

6) Maybe your windows based keyboard is the reason the boot menu doesn't show up
Borrowed an Apple keyboard and what do you know, that was exactly the reason the boot menu didnt show up when holding ALT (option) during boot. Let's try installing el capitan from bootable USB. Start up imac, hold option key, boot menu shows with "install el capitan". At the end of the installation progress "an error occured, try restarting the installer".

7) Maybe 10.11 is too far. Let's try 10.6 now that we can finally boot from the installer DVD.
I start up the iMac, hold option key, erase the disk and run through installer and it freezes at "18 minutes left". Tried the USB instead, now it does finish but errors out with "OS X can't restart your Mac. Quit the installer and try again".

8) Try installing El Capitan (clean) on a different device then plug into iMac.
Installed El Capitan on MB Pro 2011, took out the SSD and mounted in the iMac. It does boot, gets to login screen and then just a spinning rainbow wheel of death.

Any ideas?
You name it, I've probably tried it. I will edit opening post throughout the discussion. I'm starting to believe either the motherboard or GPU is faulty.
 
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There has been an issue in the past (not sure when it started or which models are affected) where booting from a USB SSD results in long delays during the boot. Once the desktop comes up, however, everything runs full speed. I was wondering if your 5 minute login was a result of this.

I can't tell from what you wrote if you have opened up the iMac or not. But if I'm reading it correctly, you installed a fresh copy of OS X Leopard on a USB drive and the iMac boots from it without the white screen.

Since you said the internal hard drive failed or is failing, and since we know the iMac works when booted from a different drive, why not just replace the bad drive with a new SSD, install El Capitan, and call it a day?
 
That's exactly how my Leopard installation was acting on the iMac: very lengthy login load and then normal performance after that. Although not the main problem, very interesting to know it can be caused by external installation.

About the successfull Leopard boot: I've taken a second empty SSD somewhere from my stock and installed Leopard by connecting it through USB (SATA -> USB adapter) into a MacBook Pro 2011 (with the Leopard installer USB connected by USB - yes everything was external). After the successful installation I mounted the SSD internally into the iMac and it boots fine (except for long log-in load).

Regarding simply installing El Capitan on a SSD and mount it into the iMac, well it's impossible to install EL Capitan for me for some reason FROM or ON any device so I gave up on that. I chose a different route, see below.

I eventually cloned the failing HDD (with El Capitan) to a fresh SSD and boot it from a MacBook Pro Retina without any problems. This means the SSD with El Capitan on it is working and not corrupted. With much optimism I mounted this SSD into the iMac and bam, exact same problem: loads to 80% and jumps to white screen just like with the failing HDD!
 
Cloning a failing HDD and successfully booting it on a different Mac does not necessarily mean the cloned copy is not corrupted. What if the video driver for your model iMac was on a corrupted sector, and that file isn't even used when you boot it on your MacBook?
 
smirk said:
Cloning a failing HDD and successfully booting it on a different Mac does not necessarily mean the cloned copy is not corrupted. What if the video driver for your model iMac was on a corrupted sector, and that file isn't even used when you boot it on your MacBook?
Click to expand...
Excellent feedback. I wish I could find a way to install el Capitan clean so I could test it.
 
Install El Capitan onto the SSD while connected to your MBP via USB. Then physically install the SSD into your iMac via SATA.

Or physically install the SSD into your iMac via SATA, then fresh install El Capitan from a flash drive or from over the Internet.

Obviously, make sure the drive is formatted with the correct file system for your computer and OS: HFS+ or APFS -- not however the drive was formatted when you bought it.

If I had a failing hard drive, the only thing I would clone from the failed drive would be my data. Never the OS - best to reinstall that from scratch.
 
smirk said:
Install El Capitan onto the SSD while connected to your MBP via USB. Then physically install the SSD into your iMac via SATA.
Click to expand...
I just tried this. El capitan install USB made through terminal. Booted into installer with SSD connected to same MB Pro 2015. Installation starts, reboots system, continues installing and errors out "No packages were eligable for install. Contact the software manufacturer.."
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I suspect something is wrong with whatever dock or case you're using to connect the SSD to the MBP, or the installer is rebooting into the MBP internal drive, or something like that.

What happens if you boot the iMac while holding down command-option-R (it may take a while)? If that works then you can install over the Internet.
 
smirk said:
...

What happens if you boot the iMac while holding down command-option-R (it may take a while)? If that works then you can install over the Internet.
Click to expand...
OP has a 2008 iMac, which cannot use Internet Recovery. The oldest Macs that can do that are 2010 models.
 
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I just found out the reason why I can't install El Capitan. October 24th this year, all OS X / MacOS installer certificates have been reset. I need to download a new El Capitan .dmg from the Apple website.

After this I can finally try a clean installed El Capitan on the iMac to rule out any corrupt OS causes.
 
There are a bunch of things you could try.

Is the failing HDD still in the Mac? If so, i would remove it. Install an internal SSD, it will be a lot quicker than running anything external.

You can boot your iMac from your MBP's drive using Target Disk Mode.

If you really want to run it externally, you could use one of your other Macs to install El Capitan on an external drive or the iMac using Target Disk Mode.

If doing it externally, use FW800 over USB. It would probably run a bit faster.

There are a few other options if you really want to keep things external, but still wanted a fast drive, such as using a software RAID0 using external drives.

I would just keep it simple and replace the internal drive with a SSD.
 
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Reactions: smirk
@vertical smile Failing HDD is already in the trash and has been replaced with several SSD's. I didn't have the intention to permanently work with an external drive. I need a working system with an internal drive.

I finally managed to install El Capitan on a SSD using my MB Pro (via USB El Capitan installer). After this I've mounted the SSD in the iMac (internally).

I get the same white screen after 80% load but after some time it actually jumps into the login screen but immediately to a rainbow spinning wheel of death without a password bar.
 
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I am trying to follow the thread, but am unclear about some things.

Did you try booting from an external drive with 10.11 installed? I see that you were successful doing this with Leopard, and I see in the last post where you tried doing this internally, but have you tried booting with El Capitan externally using an external drive or another Mac?

Also, try putting your iMac in Target Disk Mode and booting another Mac from your internal iMac drive.

This might rule out some things.
 
@vertical smile: I have tried booting 10.11 (capitan) externally via USB on this iMac. Mac turns on, I keep ALT pressed, white screen, nothing.

I found out that the only way to get Capitan clean on this device is to install 10.5 (leopard) and then walk through all updates up to El Capitan.

I have Leopard (10.5) installed on iMac and it's working. To upgrade to to Snow Leopard (10.6) I need a DVD so I ordered one. I tried my 10.6.3 DVD but that doesn't work: prompts a reboot and says it will continue after reboot, but doesn't.
 
So I want to manually upgrade step by step from 10.5 to 10.11. Right now 10.5 is installed. I'm trying to boot from a 10.6 installer USB, but the iMac just ignored the pressed ALT key and boots into 10.5.

There is nothing wrong with the installer USB as it does show up in boot menu on my MBPro 2015 although it crashes into "unsupported CPU" obviously when I choose it.

Any ideas? 😭
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Also when I try to run the 10.6 installer from within 10.5, it nicely loads up and says "installer will continue after restart" after which it reboots and just vanishes!
 
things like an smc and nvram reset have already been tried I presume.. ?

It could indeed otherwise be perhaps a dead GPU, or logic board.
But also tried another stick of ram memory ??
 
FlorisVN said:
It could indeed otherwise be perhaps a dead GPU
Click to expand...

I was thinking this too as I have seen Macs display the same symptoms with GPU issues, but the OP was able to boot it in 10.5.

Maybe later OS versions could be more sensitive to GPU problems?
 
FlorisVN said:
things like an smc and nvram reset have already been tried I presume.. ?
Click to expand...

OH...... My ...... God...

The typical useless attempt you usually always ignore. The step in every troubleshoot you ALWAYS skip... It changed everything... It brought an end to 3 days of endless research, pain and suffering which involved even accidently formatting my own drive.

It was the NVRAM.

I want to be happy but I'm too tired. I'm leaving this house now. I need a drink..
 
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