iMac (24-inch Early 2008) Black (and White) Screen of Death After Software Changes

[Hurry]

Subject: iMac (24-inch Early 2008)
OSX 10.11.6 (El Capitan)

Current State: Alternating White and Black screens of death. Crashes and reboots on: Normal Boot, Recovery Mode, Diagnostics, Boot to Installer.

History: Employer's old personal computer. I need a "middling" generation Intel Mac for its Fireware capabilities so I can Target Disk mode installs. I was asked to go over what's on the hard drive and back anything up from Documents folders before I wiped and took it over. However, not one of the four people who had login accounts on this computer remembers his or her password. There is a password free Guest Access account.

When I started this computer worked fine. I was able to log in with the Guest Access account, and left the computer running for hours at a time without issue.

When it stopped going fine:

I booted to recovery, opened terminal, and ran the resetpassword command on the four user accounts.

1. After reboot I logged in successfully as User 1. Was asked about Keychain access, chose the option to update the keychain on the first user and the computer went to a white screen "your computer has a problem..."
2. Tried the next account, this time I said create a new keychain. Same problem.
3. Tried the next account and it white screened after login.
4. Tried again and it never got to the login screen: White screen.

Booted to Recovery Mode and did a repair on both disk and permissions (both reported errors).

Reboot - black screen sometimes, other times white screen. Now I cannot bring up Recovery mode without a black screen/reboot. If I boot with Option I can select Recovery Mode but I get a black screen.

Cleared NVRAM.

Boot with Option Key, select a fresh El Capitan installer USB... black screen (x2 or 3).

Tried booting to diagnostics (both D and Option+D), black screen reboot.

I have been working with computers for 30 years. I refuse to accept that a sudden, shocking hardware problem occurred right at the time I started messing with the software. The coincidence is too much for me to accept.

Any thoughts?

 

[Certificate of Excellence]

Pull out a firewire cable and utilize target disc mode. Manually pull any files you can find (assuming the hdd is not failing or corrupt) from the target mac onto your functioning destination mac, then reformat & clean install. Leave all that janky BS the previous users left you with. Truthfully if they're so uninterested that they couldn't be bothered to remember their password, then data loss is on them. You did your part. - hardware failure absolutely occurs (on a 15 y/o imac no less) and corruption happens. If they're pissy about it, pull the HDD and give it to them (or give the machine back to them) and let them figure their rats nest of dumb F-ery out.

I know that sounds kind of harsh, but really - is it your responsibility to remember their passwords or to try and retrieve their data? If anything, your only responsibility is data destruction which can be very easily remedied.

 

[Hurry]

Pull out a firewire cable and utilize target disc mode. Manually pull any files you can find (assuming the hdd is not failing or corrupt) from the target mac onto your functioning destination mac, then reformat & clean install. Leave all that janky BS the previous users left you with. Truthfully if they're so uninterested that they couldn't be bothered to remember their password, then data loss is on them. You did your part. - hardware failure absolutely occurs (on a 15 y/o imac no less) and corruption happens. If they're pissy about it, pull the HDD and give it to them (or give the machine back to them) and let them figure their rats nest of dumb F-ery out.

I know that sounds kind of harsh, but really - is it your responsibility to remember their passwords or to try and retrieve their data? If anything, your only responsibility is data destruction which can be very easily remedied.

Right but... I'm not ready to quit. I shouldn't have mentioned the original owners they're a distraction. I could go through the hassle of tearing this thing down and replacing the hard drive... or I could make sure I have done all I can to fix the problem before going nuclear. I go nuclear at work and try and get a service up and running as fast as possible and sort out root cause later. Part of what I enjoy about tinkering with old computers is that I don't have to do that.

Hardware does fail... but how often does it magically fail after running a permission altering Terminal script followed by what were probably poor software configuration choices? I accept there's a chance that lightning struck, but it defies most of my experience. Generally speaking, failures after a change are related to the change. I'm not ready after four or five hours of troubleshooting to give up.

Thanks for the target disk mode suggestion. Unfortunately that isn't an option. Ironically that's why I'm trying to get this up and running. I only have two computers with Firewire connections. This, and the G4 Cube I want to install OSX on using TDM - that's why I'm bothering with this iMac at all.

Because it has been so long since I dealt with late 2000s/early 2010s macs, I was hoping I might have forgotten something, or someone here had dug themselves out of a similar situation and had some ideas.

 

[Certificate of Excellence]

Certainly not quitting - pragmatic. IMO it is acting very similar to hdd failure - that drive & it’s cable are 15+ years old. The last 08 iMac I worked on had a janky hdd and would boot to unresponsive white and black backlit screens& a quick SSD upgrade fixed that, restored to a backup. You are entirely correct that your efforts could have corrupted needed files in software and that drive is absolutely fine but where to go with a non functioning recovery, no TDM option and the drive stuck in a borked machine, I’m at a loss short of taking the time to pull the drive out and connecting it via ext usb caddy to poke n prod or trying to reinstall an OS using internet recovery opt-alt-cmd-r. Sounds like an early intel MacBook is a good bit of kit to have around for these sorts of trouble shooting adventures. I’m of the opinion to erase-partition and install a fresh OS or restore to a clone if you have that but per your words, you’re not ready for that yet.

Best of luck to you.

 

[Hurry]

Certainly not quitting - pragmatic. IMO it is acting very similar to hdd failure - that drive & it’s cable are 15+ years old. The last 08 iMac I worked on had a janky hdd and would boot to unresponsive white and black backlit screens& a quick SSD upgrade fixed that, restored to a backup. You are entirely correct that your efforts could have corrupted needed files in software and that drive is absolutely fine but where to go with a non functioning recovery, no TDM option and the drive stuck in a borked machine, I’m at a loss short of taking the time to pull the drive out and connecting it via ext usb caddy to poke n prod or trying to reinstall an OS using internet recovery opt-alt-cmd-r. Sounds like an early intel MacBook is a good bit of kit to have around for these sorts of trouble shooting adventures. I’m of the opinion to erase-partition and install a fresh OS or restore to a clone if you have that but per your words, you’re not ready for that yet.

Best of luck to you.

Thanks - I think my biggest problem is investing a hard drive in an '08 iMac. I was hoping I missed something I could try, sounds like I didn't. Probably better to invest time and energy in another solution to get the Cube installed and come back to this if I can't (or on a rainy day).

 

[Certificate of Excellence]

A cheap $20 120gb SSD will get you up & running assuming the HDD is the culprit which it sounds like. IIRC these shipped with Leopard & run up to elcap. Anyhow, Leopard can be found as a free dmg online. Apple also released mountain lion & lion as free DLs as well so any of those on a flash drive & you can power-option into the boot picker, select the installer & be up n running quickly.

I think an 08 iMac is worth $20-25 and some time/maintenance. Cool looking machines with nice big screens & good I/o options.

 

[Volvo242GT]

If I remember correctly, most iMacs used the 3.5" SATA drives, so, you can run anything that a pre-2013 Mac Pro uses. Back in 2020, I bought a 1TB spinner for my 2008 Mac Pro for ~$35. Is the one item I still have from that computer. Will be going into the 2009 Mac Pro 4,1 I'm picking up next weekend.