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27“显示屏,分辨率为2560 x 1440像素 Thunderbolt&MagSafe电缆附件

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No video on Thunderbolt Display, but audio works. Bad power cable?

My 27” Thunderbolt Display is having an issue where it will not display video at all upon being plugged in, or will work correctly but then go stop showing video suddenly after two or three hours of use.

Strangely, even though when the video is not working, my MacBook still recognizes it (in the sense that I can select screen arrangement settings in System Preferences and also move my mouse onto the other screen). Furthermore, the speakers and camera still work when the screen is black.

I have tried resetting PRAM/SMC and tested multiple laptops and the problem persists. I have also tried using an external thunderbolt cable. Finally, I have shined a light on the display when it is dark and I can’t see any faint images.

Two things that sometimes work to “revive” the display are plugging the AC power cable into another outlet or unplugging the AC power cord where it connects to the back of the display and then plugging it back in. I have also noticed that if I accidentally bump the AC cable where it plugs into the back of the display, this can cause the screen to go black.

What is the likely culprit here? I suspect the AC power cable, but perhaps it is a logic board issue? Additionally, if the AC power cable is at fault, where can I find the right model? I don’t want to buy the wrong one by accident and I also want to make sure I buy from a reputable seller.

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Give this a try get a ThunderBolt cable plug it into one of the TB ports on the display and your TB port on your system. It should work does the video likewise wink out?

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Thanks for the response! I already tried this and it didn’t fix the problem – the display still goes dark suddenly while I’m using it or it won’t turn on at all.

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@fearful_jesuit - It was intended to isolate out what the problem is. So by using a different cable connection we now know the issue is not the cable its likely your displays power supply or the backlight logic.

You still need to do one more test to remove your MAcBook. Do you have a second Mac which you can plug the display into. If the problem remans then the display is the issue. If on the other hand the works with not issuers, then your MacBook has an issue.

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Hi @danj – thanks for your help! I managed to get my hands on another MacBook and I am having the same issue on that one, where the MacBook says it is connected by the Thunderbolt Display doesn't turn on. Do you have any idea what my next step should be?

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Then its clear your display has an issue. Lets do this one last test. With the system connected so you know the display should have a video signal place a lit flashlight on the display at a sharp angle are you able to see the faint image of your desktop?

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Thanks for your help! I went ahead and tested it but I don't see a faint image of anything when I shine my light on the display. Strangely, the audio and the camera still work.

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Hello Dan,

I have exactly the same question. What do you mean by 'fixing display”?

Is it a logic board or something that needs to be replaced? A capacitor by chance? Thx

Update (10/14/2022)

@danj Thank for the reply

Mac -> tbcable-> display -> external hdd worked and the Hdd was found and could be accessed but still no picture.

Where does the decoder chip live, on the logic board?

Not sure where to look for the glow? I’ll post a picture in the comment below

Block Image

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If you followed the same diagnostic process: First checking the cable, then check to see if the faint image is present using a flashlight to see if it’s the video logic Vs the backlight.

Then you either need the backlight power logic fixed or the TB to video conversion logic which likely means a new logic board.

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Hi Dan! I think I did, check it out:

1) regular all in one cable - no video however everything else works including usb and speakers

2) thunderbolt port via extra link thunderbolt cable to a computer - same result, no video but everything else works.

3) flashlight at an angle didn’t reveal anything

4) logic board voltage is present both at the 24v and 12v pins.

My assumption is the logic board is dead and need to be replaced.

I have a hot air soldering station but i wonder if desoldering capacitors and using LCR meter would reveal anything

What would you suggest ?

Thank you

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If you have power on the logic board and you don’t see a faint image. Messing with the caps won’t help you in isolating the problem.

You stated using a regular TB cable between the system and one of the TB ports didn’t work either, did you try daisy chaining system to display using the displays cable and then plug in to the display TB port an external HDD or known good TB display? That way you can remove the displays TB logic.

If that worked you know the video decoder chip and/or the display it’s self (T-CON) has a failure.

Also make sure you see a glow within the display just in case the backlight is having issues.

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@groowla - I see you have a second display as well. Did you try swapping out the display assembly to see if it was faulty?

The glow is only visible when the display is intact and properly setup. In a darken room you should see the screen brighten a bit from off to on.

Review Apple Thunderbolt Display Teardown for a better view of the logic board. It is similar to the older mDP 27” Cinema Display

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@danj I actually have 4 broken displays and one fully functional.

If i take the board form the functional one and try it in the broken screens will I damage the “functional” part ?

I just got the Technician guide for the display, I’ll have a read maybe I will find a clue or something in there.

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My issue with my 27" TB display, sometimes the video goes black, still with sounds, then i just replug the adapter and it works again. Sometimes the screen flickers.

Not sure if this is helping, i placed a fan under the right side of the screen, im assuming the heat is making the screen flicker or turns off.

I think my question is, is this a logic board issue or power supply issue?

Thank you!

Thunderbolt 3 type C to Thunderbolt 2 adapter (new)
MBP 2019

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@jujoe - When the displays video is lost do you see the faint image of your desktop and its icons when aiming a flashlight into the display at a sharp angle?

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Hi Dan, right now the screen is flickering. when it goes black again, ill check it. But if that is the case, what is the problem?

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@jujoe - If you can see the fault outlines of the objects that points to a backlight issue which is independent of the LCD panel logic or the graphics driver logic on the logic board.

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@danj right now, more on flickering, so i can't see the backlight.

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@jujoe - Flickering could be either a panel issue per a backlight. Need to wait till you get a black screen to tell which.

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