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Old 05-24-2021, 02:26 PM   #1
waakye
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Default Apple Cinema Display A1267 no backlight no image on the screen

Hi all,
I have this Apple cinema 24 inch A1267 that randomly stop working. I opened it up and noticed the the fan was not spinning when there is AC power. I disconnected the lvds cable feeding the matrix board and the logic board and the fan started spinning and all voltages at the test points on the logic board are available. The moment I connect the 20 pins lvds cable to the matrix board which is located in the LCD panel, all voltages at the test points goes to 0volts. Seem that the 11.88 volts is somehow shorted. Any help will be appreciated.
Thanks
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Last edited by waakye; 05-24-2021 at 02:29 PM..
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Old 05-25-2021, 06:56 AM   #2
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Default Re: Apple Cinema Display A1267 no backlight no image on the screen

Any help guys.
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Old 05-25-2021, 12:36 PM   #3
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Default Re: Apple Cinema Display A1267 no backlight no image on the screen

Can someone help me out.
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Old 05-27-2021, 05:41 AM   #4
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Default Re: Apple Cinema Display A1267 no backlight no image on the screen

No help. Nothing
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Old 06-02-2021, 02:53 PM   #5
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Default Re: Apple Cinema Display A1267 no backlight no image on the screen

The mating board on the backside of the display is the 't-con' board (I think it stands for timing controller board).

They are usually dirt cheap and have seen them new for about $10-$12 on Aliexpress. Had some good dialog with a reseller of such boards and associated display test tools but will need to do some digging.

We also have repaired the boards in the past by simply replacing each and every polarized capacitor (tantalums) onboard. After replacing about 5-10 caps (Arrow) - the display worked like new.

In a quick review of your t-con board, do not see polarized caps onboard but rather non-polarized ceramics. Usually ceramics are work horses.

You can do some testing as follows:

1) power down the board
2) meter in resistance mode
3) black probe on meter to ground on this t-con board (shield is ok)
4) red lead on each cap you can find on the board. One side should report close to 0 ohms = that will be the ground side. Otherside should not be so close to 0 ohms.

Report any oddity you see in the resistance review.

Any burn / cracks marks on the chips ?

Also, you can use diode mode on meter and then confirm each 'Dx' = diodes are ok on the board.

Update - I think I found the store on Aliexpress - this vendor has some really cool tools.

https://www.aliexpress.com/store/gro...1ce8687dHH7hhK

Best to ping him using the Aliexpress app on your phone and give them your details of the display (actually the same pic as shared here is ok). The LG p/n is what is required.

They also have stand-alone test tools to allow your PC to drive this display (ie. without your mac):

https://www.aliexpress.com/item/1005...archweb201603_

Last edited by mon2; 06-02-2021 at 03:03 PM..
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Old 06-02-2021, 03:02 PM   #6
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Default Re: Apple Cinema Display A1267 no backlight no image on the screen

You need a power supply with limiting current.
Inject power on the line that is shorted limiting the current to a couple of amps and use your finger to detect the offending capacitor (most of the times) or whatever it is.
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Old 06-02-2021, 06:07 PM   #7
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Default Re: Apple Cinema Display A1267 no backlight no image on the screen

Thanks mon2 and Dumah Brazorf.
I went through the measuring of the capacitors with reference to ground (shield of the panel) I did not see any oddity in resistance except one capacitor that reads OL on one side and 0.00volt on the other side.
What is weird is that when I connect the 30 pins connector to the t-con board, the Apple Cinema display fan spins without issue and all voltages on the test points on the logic board are all accurate with respect to the apple cinema display technician guide.
It seems that the moment I connect the 20 pins lvds cable, all voltages on the test points drops to nearly 0volts. The fan stops spinning and I heard a noise that something is overloading the circuit. When the 20 pins cable is removed, the fan starts spinning and all voltages on the test point on the logic board are available and accurate.
So do you guys think it's in the T con board.

@ Dumah Brazorf. I do not have a bench power supply for this test. Is there another way I can do this?


I really appreciate your help on this.

Last edited by waakye; 06-02-2021 at 06:11 PM..
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Old 06-03-2021, 03:56 PM   #8
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Default Re: Apple Cinema Display A1267 no backlight no image on the screen

Check also for shorts on the cable. Nearby pins. Power and ground use multiple pins.
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Old 06-09-2021, 05:00 AM   #9
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Default Re: Apple Cinema Display A1267 no backlight no image on the screen

Dumah Brazorf, what do you mean by: "Power and ground use multiple pins."
Thanks
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