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27" display with 2560 x 1440 pixels resolution Thunderbolt & MagSafe cable attachments

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Display turn Black, after many times turn off and on, sometimes works

My Thunderbolt Display (A1407) stays black after connecting it to my iMac.

After many times unplug the power cable and plug it in again, the picture came back. Unfortunately, it disappears after 30 minutes and does not come anymore. The picture was good, no mistakes.

What could it be? Power cable to the iMac or power supply?

Has anyone else had this problem and how did you fix it?

What would be the most sensible to replace?

Many Thanks

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Try this: Take a flashlight and after turning the display on and plugged into your Mac place the flashlight against the screen at a sharp angle. While faint can you see any of your desktop icons? If you do then we know the issue is within the backlight logic.

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Hi Dan, i try it with the flashlight, but i see nothing, its only black. :/

thank you for the note.

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OK, so we know its more likely a power issue within the display then.

Have you tried another power line cord and made sure the outlet is good? And does the MagSafe cord have power when you use it, the cord LED lit?

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Hi Dan,

I have try an other power line cord and it was the same. yes the magsafe is working when i put it in my macbook. and the powerpoint is well, i try other and there was all the same.

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HI,

I have now tried the new thunderbolt cable, and unfortunately it did not work, the imac recognizes that a thunderbolt display is connected, but it is still black on the display.

sometimes it works, if I leave the Thunderbolt display turned on for a few hours, then turn it off briefly and turn it back on, then comes the picture for maybe 20 minutes.

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I'm thinking you have a bad Thunderbolt cable here. It's the only logical thing that fits the fact your displays fan & MagSafe cord are powered. It turns out you can plug in a Thunderbolt cable into the external ports and the display into your Mac. See what happens then.

Update (11/26/2017)

mmm... You do have me scratching my head here. You have removed the usual suspects.

At this point it needs to be something on the logic boards power circuity that needs attention. This is beyond a DIY as you need to have access to the schematics and understand how to troubleshoot at the component level. Even then you'll need to find a replacement part and have micro-soldering skills.

The other direction is to just replace the logic board while expensive it's a lot easier!

A1407 27" Thunderbolt Display - Logic board Apple P/N 820-2997 ($192.00)

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I have now tried the new thunderbolt cable, and unfortunately it did not work, the imac recognizes that a thunderbolt display is connected, but it is still black on the display.

sometimes it works, if I leave the Thunderbolt display turned on for a few hours, then turn it off briefly and turn it back on, then comes the picture for maybe 20 minutes.

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@mark4aid Before replacing the logic board you'll want to follow step 10 in the technician guide (page 25):

"Remove LCD panel. Set digital multimeter to DC and correct range, and verify that a 23.3–25.7 V DC voltage is present between logic board test point (24 V DC) and chassis ground (GND)."

My guess, since your issue is intermittent, that you're going to see that you have 24V and that your problem is the LCD itself. If it's getting 24V then it's not the logic board.

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I've never seen a power cord go bad like that, but since it's the easiest thing to try, you may as well try another one. Another thing to check would be if the display appears on the iMac when plugged in. Last time I looked at one of these it was rather hard to tell that there was a display when using a flashlight on it until I started moving the mouse around. I realized that the Mac was detecting the display and outputting an image but the backlight wasn't working. This particular monitor would slightly flicker when plugging it into the Mac.

If you're absolutely certain there's no powering on, then it may be the power supply. Here's a link to the Apple Technician Guide for this model.

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Hi,

I tried that with the flashlight, but I can not see anything. When I connect the Thunderbolt display to my Imac, I see on the Imac that the thunderbolt display has been detected. And also the fan of the thunderbolt display does, I can feel that with my hand. if I connect the magsafe connection of the thunderbolt display to my macbook, then load the macbook with current.

yesterday I had the thunderbolt display long connected, picture was the whole time black, then I have the thunderbolt display briefly disconnected from the storm net and plugged in again and he has done. However, I have to say that the image of the thunderbolt display is set to the highest brightness, and it is much darker than when I set the highest brightness level on the imac.

could it also be due to the thunderbolt cable?

I'll test that tomorrow, with an external thunderbolt cable.

thank you

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@mark4aid In the Apple Technician guide the next troubleshooting steps involve disassembling the display and verifying connections. In my case I was eventually able to detect a very faint image when I moved the mouse cursor over to the screen. I verified the backlight voltage of the logic board and all cable conditions and connections, hence the only thing left was the LCD panel itself. I looked into replacement panels and they were more expensive than the display is worth. I did find quite a lot of anecdotal evidence of backlights failing in these displays after about 4 years or so. It sounds like it's your LCD panel.

There may be a way to repair the failure, but that's beyond the scope of my knowledge (and Apple never bothers to do stuff like that, they just charge an arm and a leg to replace the part so that you'll just buy a brand new display instead).

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I don't know if this comment will help anyone, but not sure where to post my "epiphany". My 30" inch Apple Cinema display after having been turned on for a while would suddenly turn off for several second and then back on. It would do this continuously, really frustrating trying to get some work done. As it turned out, this problem was the monitor getting hot, I clipped a simple 6" fan (from Target) to my desk blowing across the back of the monitor, monitor stayed cool and it solved the problem. Hope this helps someone.

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