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Screen Dies (Blacks Out) Randomly???

G

galaxy7

macrumors regular
Original poster
Jan 18, 2014
103
2
Hey everyone...my iMac is giving me some grief! A while back, I started getting flickering on the screen as if it was trying to adjust for the light or something like that. It'd flicker a few times and then stabilize and you could go about your business. That continues. It's more of a nuisance than anything. But that's not the real problem (although it's probably an indicator)

Now, at least once per session, the screen just ups and goes completely black; turns completely off. Be patient and wait about 15-20 seconds and hit the power button on the back of the iMac will turn the screen back on and you can resume life.

Now here in the past few days, both are progressing. The brightness of the screen almost continually while in use, flickers in intensity and the complete blackouts are getting worse. A few times, the power button trick did not bring it back. Had to force a shutdown and unplug it and walk away. Then a restart would eventually bring it back.

Certainly seems like she's on her way out.

But the colors on the screen are working and the computer itself is working and functioning completely normal...no problems at all.

Am I looking at a new computer or is this something that can be addressed??? Where can I take it/send it for this problem?

Thanks everyone!!
 
galaxy7 said:
Hey everyone...my iMac is giving me some grief! A while back, I started getting flickering on the screen as if it was trying to adjust for the light or something like that. It'd flicker a few times and then stabilize and you could go about your business. That continues. ...
....
But the colors on the screen are working and the computer itself is working and functioning completely normal...no problems at all.

Am I looking at a new computer or is this something that can be addressed??? Where can I take it/send it for this problem?
Click to expand...

An Apple store would be a good place to start :D

Your symptoms likely mean that the backlight is failing.
When your screen goes dark - can you still see dim video on the screen? Shine a bright light into the screen, particularly on areas where you should expect to see images, such as the dock, or the menubar.
If there is no image at all, then likely the graphics card is failing, but could also be the LCD panel.

Which iMac do you have (How old is it?)
 
It's the smaller iMac and I got it for Christmas in 2009.

I haven't tried the flashlight thing, but when it happens, it's completely black/off/out; there's nothing dim or visible by eye with the ambient light already in the room.
 
galaxy7 said:
It's the smaller iMac and I got it for Christmas in 2009.

I haven't tried the flashlight thing, but when it happens, it's completely black/off/out; there's nothing dim or visible by eye with the ambient light already in the room.
Click to expand...

You may be correct, if the screen completely black - but ambient light may not be bright enough to check. be sure to try a bright flashlight.
Your issue CAN be caused by heat. Be sure to check that the cooling vent on the back is clean and clear (above the AC cord, but below the hinge). That's very often missed...

If I had your iMac, I would try an external display. If the video on the external is bad, then it's likely a logic board, or a video card, the integrated (Nvidia) graphics is not a replaceable part, only the logic board. If you have the ATI Radeon, then that card is replaceable.
If the external works OK, then it can be the backlight board, or the LCD panel (still fairly expensive, when I last looked for one)
You can also search for the service manual, and do some other troubleshooting, ... Search for "imac_21_late09.pdf"
 
Thanks for the great tips. Vent is clear. Will try the flashlight thing next time it happens. Don't have another monitor to try, so if it continues (which it will), I'll report back with the flashlight and see where we're at. I don't recall what logic board I have. Most likely what came stock as the computer was a gift and I know they didn't splurge for anything (graphics card) that would have been an upgrade as there's no need.
 
OK...just had an episode and it was one where the double tap on the power button didn't restore the screen. Screen was completely black! Grabbed the flashlight and lo and behold, i can see everything on the screen. Can even move the mouse around and do anything you can do when the screen is fully lit.

So you're saying this is a backlight? Is that replaceable? Expensive?

Thanks for all the help!
 
DeltaMac said:
Most likely failure is the backlight board.
Apple's part number for that is 661-5304
Example for price (but check for yourself)
http://www.powerbookmedic.com/Intel-iMac-215-LED-Backlight-Board-p-21648.html
Click to expand...

Deltamac...do you know if this part is internal to the screen, or just internal to the computer. My issue is getting worse but haven't had time to take it anywhere yet. I pulled the screen out to check the obvious stuff today (wires, connections, etc) and found nothing obvious. After reassembly, it worked great for an hour or so and then off again. If this board is being the screen, then certainly within my capability to swap it out. Just don't think I'd want to tear into the screen itself.
 
No, the LED backlight board is inside the iMac, and not internal to the LCD panel itself.
This iFixit repair guide will show you where it is: https://www.ifixit.com/Guide/iMac+Intel+21.5-Inch+EMC+2308+LED+Driver+Board+Replacement/1768

This is assuming that you have the 21.5-inch Late 2009.

If you have the slightly older 20-inch, then you may need to replace the inverter board. Again, that's not internal to the LCD panel, but is somewhat more difficult to replace.
 
Awesome stuff! Thank you again so very very much for all the help. One final question...with my symptoms, do you think it's worth the ~$50 to throw a board at it?

Worst case and it's not the board, then it's most likely something with the screen itself right? And in that case I'm hosed anyways?
 
OK!
5 years old or so. It's had a good life (right?)
If you are looking for a reasonable excuse to move to something newer, then, no, it's maybe not worth even $50 more to repair.

If it's generally working OK for you, and you are still satisfied with the iMac's performance, and it does what you want it to do - then ~$50 is way less than replacing it completely.

But - you ask, "what're the odds that card will fix it?" Not 100%, but I would go with 90%. It's pretty likely that will be all you need.
 
Thank you again! Yes...there is absolutely nothing wrong with this machine; nothing. It completely meets my needs and there's been zero noticeable degrade in performance nor any bugs showing up over its life. This is the first fit it has given me since day one. CD's get stuck every once in a while but I know how to eject them and don't use them that often anyways.
 
Well, thanks everyone, but unfortunately the board did not fix the problem. New board installed and the screen continues with the same symptoms. Light struggles to come on and can see the screen with a flashlight.

Any suggestions on what's next??
 
galaxy7 said:
Well, thanks everyone, but unfortunately the board did not fix the problem. New board installed and the screen continues with the same symptoms. Light struggles to come on and can see the screen with a flashlight.

Any suggestions on what's next??
Click to expand...

If it's not the LED driver board then it can only be the backlight itself or the cable used to power it. Your only option at this point is to replace the panel entirely.
 
Is that even an option/possibility to replace the whole screen? Where's a good place to shop for that, if available?

And it was mentioned earlier this could possibly be a heat problem. I'm guessing since I have these symptoms even after the computer had been completely shut down, heat is most likely not the problem.

Looks like screen 661-5303 is available from a few places for around $200 used. Is this what I need? Thanks again everyone.
 
Last edited:
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