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Model A1419 / Late 2013 / 3.2 & 3.4 GHz Core i5 or 3.5 GHz Core i7 Processor, ID iMac14,2

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Backlight LED strip stopped working

I have iMac 27” late 2013 model. My backlight stopped working and display works just fine. Replacing the display at Apple shop will cost me around $1000. I'm trying to find the solution just to fix backlight since screen is working perfectly, without a scratch on it.

I had a friend look at it (he fixes Macs) and he told me that LEDs in backlight strip stopped working.

Can I buy that strip from somewhere?

Display model is LM270WQ1 SD F2. I can find SD F1 but this one not.

Any help is appreciated!

Ответ на этот вопрос У меня та же проблема

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I don't have Apple keyboard. Pressing D on standard keyboard doesn't work. Do I need to press combination of two keys?

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Just ran the diagnostics, it said No issues found reference code ADP000.

Any suggestions?

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Thats good! ADP = Apple Diagnostics Program - Zero

You would think a user based diagnostics would just give you: No problem found ;-}

Do keep in mind diagnostics is still limited on what it can do as it has limited sensor logic to poll. The backlight logic is beyond its ability to access.

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Lets backup here a bit… There are three parts involved in the backlight

  • Power supply
  • LED driver logic on the logic board
  • The display its self

If we think this through, the LED’s within the display are driven in sets, so if one LED had died then the other LED within the given set or even the other sets would be lit. So the display is the less likely the issue here.

That leaves us with either a power supply or LED driver logic on the logic board. So how can we isolate this down? Have you tried running the onboard diagnostics? Restart your system and press the D key. Your external monitor won’t display so you’ll need a flashlight aimed at the display so you can make out the screen and the steps. Did you get an error message? Let us know.

One of the things we have seen is the newer ‘Thin Series’ iMac power supplies tends to be more sensitive to power fluctuations. I do strongly recommend using a good fill-in UPS and use surge suppressors on all your gear so there is no unprotected connection to your system either USB/Thunderbolt ports or network via Ethernet.

So, replacing the power supply is quite easy, but fixing the backlight logic on the main logic board will take some skills. It could be as simple as a blown fuse.

One last point I’m assuming you haven’t opened the system if you had at some point, you could have a damaged display cable or the backlight power cable.

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Thank you for such detailed answer!

I hope this helps before I debug everything - screen flickered and friend told me that LED strip bulbs were half not working.

One thing that I do notice is that display is working and if you point flashlight on display you can clearly see everything working it just doesn't have light.

Does this narrow it down?

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@davidpetrovic91 - Did you run diagnostics yet?

I'm leaning towards the LED driver logic from your new info.

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No Dan, I'll do it as soon as I get back from work. I didn't read everything in detail first time and I did it now.

I'll run debug and let you know what is says. Thanks a lot!

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Yep! You have a logic board issue within the backlight driver logic. This will take some deeper skills to narrow down.

Again, it could be a simple fuse that blew (did you take the display off at some point?) the driver chip could have burnt out (power surge). You'll need to find someone locally that has the skills to work off of schematics and boardview drawings and has access to the needed micro-soldering tools and lastly, the needed SMT parts to fix your system.

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@danj thanks! Would it be possible to replace the logic board if I can't find someone with those set of skills?

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the Power supply ic, some Diode Filter Coil is damaged, perhaps

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