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Model A1311 / Mid 2010 / 3.06 & 3.2 GHz Core i3 or 3.6 GHz Core i5 Processor

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On boot: backlight lights up, then goes dark after half a second

I’m trying to repair an iMac 21.5” (Mid 2010) EMC 2389. It has two symptoms:

(1) When I press the power button, it chimes a few seconds later, then the backlight lights up on a grey display, then the backlight goes dark immediately (a half-second later). If I shine a flashlight at the display, I can see the Apple logo as it’s trying to boot.

(2) When the iMac tries to boot, it shuts down after about ten seconds.

I’m guessing (2) is because of a bad hard drive, so I’d like to find a solution to (1). Here are some more details:

(1a) If I hold Option as I turn it on and then shine a flashlight at the screen, I can see a hard drive icon as it waits for me to select what to boot from.

(1b) If I connect an external display, I don’t get any signal on it This is probably okay as it doesn’t reach the point at which it tries to initialize the graphics chip.

I thought this would be a simple issue of the LED power board being dead. So I purchased and installed a replacement LED power board, but I get the same symptoms.

Anyone have any suggestions for other things I could try?

Edit:

It chimes once when it boots, before the backlight flashes on then off.

If I hold Option when it boots, it will sit at the boot volume selection screen (as verified with a flashlight) forever without turning off. That’s why I think that the turning off when booting is some problem with the internal drive, and if I were to boot from an external drive it would probably boot all the way - but probably leave the backlight off.

Anyone have any suggestions for what could be wrong with the backlight, and how to fix it?

More details:

- If I hold down Command-R during boot, the iMac boots into Recovery mode and gives me the usual prompt to restore from backup, reinstall macOS, run Disk Utility, &c. (I can see all this with a flashlight pointed at the iMac's display.) At this point, my experience on other Macs tells me that it should have enabled an external display; but with this iMac, the external display remains dark and doesn't see a signal.

- There are only three times when the iMac's display backlight turns on for half a second: when it first boots, when it initializes the graphics chip (I call tell because this happens partway through booting into Recovery mode), and when it wakes the display from sleep (after I let Recovery sit for a while and then I press a key on the keyboard).

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Please tell us exactly what part you replaced.

I replaced the LED backlight inverter board with part 661-5537, which was slightly different than the part I was replacing (more capacitors, metal pads on the underside of it) but was listed as being compatible with a mid-2010 iMac 21.5" A1311.

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Here's a set of helpful links on how to create a bootable OS installer drive and how to startup using it:

- How to create a bootable macOS Sierra installer drive

- Mac startup key combinations

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Let us know what happens when you boot up using the external drive, then try the external display. That will give us the needed clues to figure this out.

Will do, thank you! I'll update when I've done that.

Getting a bootable macOS HD is a challenge - my other Macs are running Mojave and won't run the High Sierra installer (I can download it from the Mac App Store; they just refuse to run it).

But I have these details:

- If I hold down Command-R during boot, the iMac boots into Recovery mode and gives me the usual prompt to restore from backup, reinstall macOS, run Disk Utility, &c. (I can see all this with a flashlight pointed at the iMac's display.) At this point, my experience on other Macs tells me that it should have enabled an external display; but with this iMac, the external display remains dark and doesn't see a signal.

- There are only three times when the iMac's display backlight turns on for half a second: when it first boots, when it initializes the graphics chip (I call tell because this happens partway through booting into Recovery mode), and when it wakes the display from sleep (after I let Recovery sit for a while and then I press a key on the keyboard).

Does any of this help diagnose it?

@bkendig - Sorry for missing your update post.

If you can see the faint outline of the desktop then that tell us the backlight logic needs repairs. It could be a simple as a blow fuse or needing a new LED driver board.

As far as the external display not showing up that could be because you are using a Thunderbolt cable instead of a miniDisplayPort cable or the adapter for your display is bad. Your external should be working here! As the internals issue is backlight not display signal.

BUT!! I'm working off the idea you are using MacOS not Ubuntu. Ubuntu adds a complication! As you need to have the needed video driver setup and working.

So... I strongly recommend you get back to OS-X/MacOS that your system supports. I do strongly recommend you stick with Sierra on this model. Yes, High Sierra will work but it has problems with SATA based SSD's running APFS file system which will upgrade automatically when you install it and you can't undo it without redoing the drive.

Thank you for your informative comment! I am in fact using a Thunderbolt cable - I didn't realize that wouldn't carry a video signal!

This computer has macOS on its hard drive (just turns off when trying to boot from it). I tried to use an Ubuntu flash drive, but the computer won't see that as an option to boot from for some reason, so I abandoned that line of thinking.

I did replace the LED driver board (with this: https://www.ebay.com/itm/661-5537-Genuin...) but that didn't change the situation at all; same behavior. Next I'll make sure that the other ends of the three cables to the LED board are good. Do you have any other suggestions for what I could try?

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Try an external hard drive with an apple operating system installed… If it’s not your hard drive plug it into an external monitor and if you get a picture it’s not your hard drive. I don’t know how many chimes you got but that could also be the ram.

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Thank you! I've actually got a flash drive with Ubuntu on it that I can try booting from. But I updated my post with a few details - I suspect that I'll be able to successfully boot from an external drive and get it to work with an external display, but I'd like to be able to fix the internal backlight; do you have any suggestions for what might be broken with that?

(The iMac chimes once when it boots.)

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As Gerald said,you can try that option. But the fact it goes dim like that makes it seem like a component issue. As for connecting to an external display,it won’t display until it fully boots up. The hard drive is what has the drivers for that generally anyways. So it wouldn’t do that yet. With a desktop,it is designed to output to a monitor,period. A laptop or Mac is designed to display to its internal screen first. Displaying externally is a feature and requires appropriate drivers for that.

Jessa Jones is very good at these repairs. She specializes in iPhones. She has repaired macs before. You can contact her at ipadrehab.com if you need to. She has good pricing,and is very popular amongst the apple repair community on ifixit soldering.

She fixes quite a lot of iPhones that have no backlight. It’s usually the filter that blows and leaves an open line(meaning one point to another for electricity is broken). This is a very common causs for backlight. Have you taken the hard drive out? If so,does it still $@$* down after 10 seconds?

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Yes we know Jessa, but was unaware she had moved into iMac repair https://www.ifixit.com/User/Activity/197...

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