Screen not working on late 2006 iMac

[Macbertha]

The screen on my workhorse late 2006 iMac (OS 10.7.5) is on the fritz. Connected to an external monitor to trouble-shoot. Ran “Verify Disk” in Disk Utilities, which produced the message: “Storage system verify or repair failed.” Received the same message after running “Repair Disk” in Disk Utilities.

Restarted the iMac, pressing the Command and “R” keys to reach Recovery Mode. However, the iMac’s screen doesn’t appear on the external monitor. Some jiggling of the power button sometimes results in a patterned background appearing on the external monitor, but not the OS Disk Utilities menu.

Since the external monitor is initially mirroring the iMac desktop, is the problem more likely to be something other than the iMac hard drive? Perhaps the video card, the motherboard, heat sensors? What are the odds replacing the hard drive solves the problem? Has any forum member experienced this problem and found a solution?

Microsoft Word and Microsoft Excel are installed on the 2006 iMac, which is used primarily as a scanner, via a Cannon printer purchased in 2006, and as a word processor, with no internet connection. The original 250 GB hard drive was replaced in 2012 with a 500 GB hard drive. Have original OS X install disks. Hoping to avoid investing in a new printer and Microsoft software. Have a 2017 iMac for daily use.

 

[paardenkapper]

I am not sure whether you're mixing internal and external monitor in your description?
Does the internal monitor work at all? Considering the age of the system it could be a broken screen or graphics card.

 

[Macbertha]

I am not sure whether you're mixing internal and external monitor in your description?
Does the internal monitor work at all? Considering the age of the system it could be a broken screen or graphics card.

The internal monitor works for a brief time upon booting up, then goes black. Jiggling the power button sometimes results in the internal monitor coming to life, but it goes black after a minute or two.

Thanks for your reply.

 

[paardenkapper]

Do you have a second display available to test whether it works this way?
There could be a plethora of possible faults like a dying power supply, the graphics card or the screen itself.

Have you tried resetting the PRAM just as a measure which sometimes helps?
Power the MAC and then press CMD + OPT + P + R.

This helped me once with a jumbled screen on an iMac.

 

[Macbertha]

Do you have a second display available to test whether it works this way?
There could be a plethora of possible faults like a dying power supply, the graphics card or the screen itself.

Have you tried resetting the PRAM just as a measure which sometimes helps?
Power the MAC and then press CMD + OPT + P + R.

This helped me once with a jumbled screen on an iMac.

Tried resetting the PRAM in the past. After hitting the power button and holding down CMD+OPT+P+R to reset the PRAM, the screen comes on for an instant to reveal the Reset Menu (per attached image obtained online). I've found that if I unplug the machine for several hours, that it will boot up to the log-in window for 20 or 30 seconds. Upon logging in, the desktop displays before the screen goes black after 30 seconds or less.

Very much appreciate your interest and suggestions.


T

 

[Macbertha]

Update.
Found Service Manual for late 2006 iMac online. Symptom Charts indicated problem may be inverter, which I replaced. Screen still goes black after showing log-in window for a few seconds (not enough time to enter password) upon booting up.
Attached image shows the 3 Diagnostic LEDs are ON. The bottom LED indicates "the power supply has been detected by the main logic board." The middle LED "indicates that the main logic board has detected proper power from the power supply when the computer is turned on." The top LED "indicates that the computer and the LCD display are communicating. This LED will be ON when the computer is turned on and video signal is being generated." The front LED (power indicator light) comes on when the computer is booted up, but then goes off and stays off.
Wondering if this information helps anyone identify the cause of the screen quickly going black when booting up.

 

[TheShortTimer]

At this point, I'd follow the suggestion by @paardenkapper to test the iMac with a 2nd display and see what happens.

 

[Macbertha]

At this point, I'd follow the suggestion by @paardenkapper to test the iMac with a 2nd display and see what happens.

Thank you for your reply.

Mirrored the iMac to a Samsung QN90B Neo QLED 4K Smart TV (2022) in the past and it worked until it didn't!! Now, the Samsung shows that the iMac is not powered up, when it is. Sometimes the Samsung will display the background, but not the menu, when I put the iMac in Recovery Mode (Command+R).

Replaced the hard drive today with the original hard drive, which died years ago. Inserted Mac OS installation disc and followed prompts until the point that no installation volume (as mentioned, the hard drive died years ago) was found. The iMac screen stays on throughout the Reinstall Process, but the Samsung still is asking that the connected device (iMac) be powered up.

With the iMac's original (bad) hard drive installed, the screen remained operative through part of the reinstall process. That being the case, might the problem be the current hard drive? However, this doesn't seem to address why the Samsung (external monitor) continues asking that the iMac be powered up.

Thanks for any additional feedback. Certainly a mystery.

 

[TheShortTimer]

@Macbertha thank you also for your detailed response.

If you haven't already, it's worth resetting the SMC to see if that might help.

• Shut down the computer.
• Unplug the computer's power cord and all peripherals.
• Press and hold the power button for 5 seconds.
• Release the power button.
• Attach the computers power cable.
• Press the power button to turn on the computer.

I doubt very much that the issue is your hard drive. My money is on the logic board/GPU failing if your TV previously worked fine with the iMac but is now unable to detect a signal. The TV of course continues to work with your 2017 iMac/other computers? If so, then that cements my suspicion even further that the logic board/GPU is terminal.

If the 2006 model is one that you're fond of, it should be fairly easy to pick up a replacement quite cheaply and then transfer over your HDD and continue using your favoured arrangement with the printer and software. Come to think of it, they'd all work on a later iMac too. I run Office 2011 under Mojave on my MacBook Air, for example.

 

[Macbertha]

Thanks very much for your additional feedback. I tried resetting the SMC again, with no results, and my 2017 iMac mirrors perfectly with the Samsung TV.

A computer repair novice, I never opened a computer before, but I've now embraced this challenge.

Latest update. Tried, but could not replicate my earlier Reinstall Process experience. iMac screen stayed black, but the Samsung displayed bright blue screen and active mouse pointer, which I could control from the iMac. Later in the day, could replicate none of the above.

Your knowledge and diagnosis are greatly appreciated. To that end, and in the interest of educating a novice, the Diagnostic LEDs indicate that the logic board is detecting the power supply, and has detected proper power from the power supply when the computer is turned on (detailed in post #6). If you have time, can you briefly explain in layman's terms one or two critical functions the logic board/GPU is not performing.

Thanks once again.