Late 2009 21.5" iMac only boots in safe mode. Thick (inch wide) vertical lines on screen

Question

Level 1

1 points

Late 2009 21.5" iMac only boots in safe mode. Thick (inch wide) vertical lines on screen

I have a 21.5 inch iMac from late 2009. 3.06ghz processor, 8gb ram, and an ATI Raedon HD 4670 with 256mb for graphics. It's running OS X 10.8.5

A few days ago the power was unplugged on accident, and I tried to turn it on again. The startup noise sounded but the normal white startup screen was covered almost entirely by strange glitchy lines which did no move. Eventually the lines disappeared and the screen only showed a white screen. This happens every time I try to start my computer unless I hold shift and boot in safe mode. Then it starts up and goes to the login screen, but all the time there are thick vertical lines (which don't move) on the screen. Also, around the mouse pointer is a box of the same thing the lines are made of. This box moves with the mouse pointer. Graphical movements like minimizing windows also seem to be choppy.

I can only start the computer in safe mode. I tried starting up holding the D key to do a hardware test and nothing happened, just the same white screen appeared after the "glitchy" white screen went away. I also tried to do an SMC reset but nothing happened.

Here are some pictures of what I see when I try to use it:

My warranty has expired. Since I must start the computer in safe mode, can I back it up?

I'm hoping its a software issue, but it seems like the problem may be the graphics card. Any ideas?

And any fix besides taking it to an apple store, the nearest of which is almost two hours away.

Thanks

Edit*

Another thing I forgot to mention is that for the past few months before this my iMac has been shutting down randomly overnight. When i turn it back on, it says something along the lines of "your computer restarted because of a problem." I don't know if this is related, just thought I'd mention it

iMac, OS X Mountain Lion (10.8.5), null

Posted on Jan 2, 2015 10:20 PM

Reply

Answer 1

Aug 2, 2017 4:10 PM in response to K9TAXI

My late 2009 iMac started freezing on boot. Booting in safe mode showed the same erratic screen behaviors. In light of this post I elected to try the bake method and it seems to have worked. If these symptoms return I will definitely go forward to the professional reball approach. Thanks for this clearly written and thorough post.

Reply

Answer 2

Jan 2, 2015 11:13 PM in response to Gwito

It looks like to me that the graphics card is failing, that explains why it will only work in safe mode and the "computer restarted because of a problem" message.

You should be able to back it up using Time Machine in Safe mode, a backup should be your first priority!

I doubt this will work but try resetting the Pram and SMC:

Intel-based Macs: Resetting the System Management Controller (SMC) - Apple Support

How to Reset NVRAM on your Mac - Apple Support

To use Apple Hardware Test you need the disc install discs that shipped with your iMac.

If you have them insert the Applications Install Disc 2 into the SuperDrive and start the computer with the "D" key held down.

See if this yields any results.

But the way I see things, it might be time for a trip to an Apple Store😕 - Sorry

Reply

Answer 3

K9TAXI

Level 1

0 points

Jan 26, 2015 6:02 PM in response to Gwito

Gwito, I have the exact same iMac with the exact same problem. Were you able to resolve the problem?

EDIT: Thought I'd mention that I ran Tech Tool Pro (commercial diagnostics program). Everything checked out OK including the graphics card and the graphics RAM. Not a single problem found.

Reply

Answer 4

K9TAXI

Level 1

0 points

Mar 10, 2015 8:32 AM in response to K9TAXI

UPDATE: My problem has been resolved. This particular defect is the result of a bad solder joint on the GPU chip. I had to remove the main logic board and mail it in to an electronics repair technician. It seems this particular model of iMac has problems with the GPU overheating which caused the solder joint problems. The electronics technician performed what's called a BGA reball. They unsolder the GPU and clean up the pins on the chip, then clean up the pin sockets on the logic board and re-solder the chip back in. It requires specialized equipment. Some technicians will perform what's call a solder "reflow" where the just heat up the solder joints without removing the chip or cleaning anything up. In my research, I found the BGA reball tends to be a longer lasting fix than a solder reflow procedure. Both would probably work fine if the GPU overheating problem is resolved. This can be resolved by installing a fan control utility on your iMac and setting the CPU/GPU cooling fan to run at a higher rate than it would normally.

I realize there are many videos on you tube that show how to bake a circuit board in an oven, or use a heat gun to heat up the bad solder joints but these types of repairs are not always long lasting. I choose the complete BGA reball because I didn't want to have to take this iMac apart again. It's still a good computer and I can always replace components myself as needed (I have an electronics background). Now that I nave smcFanControl installed, I don't expect to have any more overheating problems.

Reply

Answer 5

Mar 14, 2015 1:19 AM in response to K9TAXI

I'm happy to hear you found a fix!

Just out of curiosity, how expensive was the BGA-reball, it must have cost a bit!

All the best

Reply

Answer 6

K9TAXI

Level 1

0 points

Mar 14, 2015 8:31 AM in response to Muufungman

The place I chose for the repair charged $318. I paid to ship is there and they paid to ship it back. I only shipped the logic board and I will say it was a job removing it and reinstalling it.

Reply