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Old 03-07-2019, 02:34 PM   #1
Misterkeeks
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Default Apple 27" Cinema Display (A1316) has trouble turning backlight on

I have an Apple A1316 27Ē Display (non-Thunderbolt) that is exhibiting a weird backlight issue.

When first plugged into a computer, when it receives a signal, the backlight flickers briefly but fails to stay on. Otherwise the monitor works fine (the computer thinks another monitor is attached, I can see that it is displaying using a flashlight).

I tried turning itís brightness all the way down before connecting it. When connected, it flickered, then stayed on. So it seems that it can barely muster enough energy to turn the backlight on, but once itís on, itís fine. Other people have had issues with no backlight after a period of functionality, my issue seems to be kind of the opposite.

What should I start testing on this? It seems like the power supply just can't handle the load it's getting all of the sudden.
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Old 03-07-2019, 08:18 PM   #2
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Default Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

If your back lights stay on, when the level is turned down to next to nothing, then one or more LED's in the back light strip could be still bad. LED's can fail like that.
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Old 03-07-2019, 08:24 PM   #3
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Default Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

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Originally Posted by CapLeaker View Post
If your back lights stay on, when the level is turned down to next to nothing, then one or more LED's in the back light strip could be still bad. LED's can fail like that.
I think maybe I provided an iffy problem description.

If I turn the display brightness all the way down before connecting the monitor (and thereby turning it on, as it has no physical button of any kind), the backlight successfully turns on, after which I can turn it up as much as I want with no issues.

Basically, once the backlight is on, things are fine. No problems.

But getting the backlight on requires the brightness to be turned way down, or it won't turn on.
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Old 03-08-2019, 10:19 AM   #4
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Default Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

This does seem like a bad capacitor on the power supply, The weak capacitor will take some time to charge to the full voltage, so by turning down the brightness/backlight will allow the cap to charge with minimum current being drawn from the circuit. Once the cap is charged, you can then draw more current from that circuit.
If the brightness is tured up at start, the caps voltage will be too low tripping the led's error circuit and shutting it down.
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Old 03-08-2019, 01:01 PM   #5
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Default Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

I agree with RJ. In order to test this, heat up the caps with a hair dryer, so the caps are warm, but not hot that you burn yourself. Then turn the monitor on and see what happens.
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Old 07-03-2019, 01:14 PM   #6
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Default Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

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Originally Posted by CapLeaker View Post
I agree with RJ. In order to test this, heat up the caps with a hair dryer, so the caps are warm, but not hot that you burn yourself. Then turn the monitor on and see what happens.
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Originally Posted by R_J View Post
This does seem like a bad capacitor on the power supply, The weak capacitor will take some time to charge to the full voltage, so by turning down the brightness/backlight will allow the cap to charge with minimum current being drawn from the circuit. Once the cap is charged, you can then draw more current from that circuit.
If the brightness is tured up at start, the caps voltage will be too low tripping the led's error circuit and shutting it down.
So, I ended up trying a replacement power supply as I got one for a lower price than they usually go. Issue persists in the exact same way.

So, next suspect I guess is the main board, which also contains the backlight circuitry. I’ve attached a stock photo of this board to the post. The backlight connector is the black plastic connector on the bottom left/middle area.

Seems like there are a lot of SMD electrolytic capacitors, as well as some voltage regulators (?) in that region. I can replace the whole board for $35, but are there any things I can diagnose now with a multimeter?

Also, is it possible that failing LEDs would require more current to start up, thus causing an intermittent failure to turn on the backlight?

I guess I’ll try the hairdryer trick on the main board as well.
Attached Images
File Type: jpeg A45969E0-86EE-4D1E-96F7-AB5CDA4358B2.jpeg (310.9 KB, 10 views)

Last edited by Misterkeeks; 07-03-2019 at 01:15 PM..
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Old 07-22-2019, 10:08 PM   #7
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Default Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

Replacing the backlight with new LED strips fixed the issue. So, I'm inclined to say that a lot of the common no backlight failures on this model stem from a failure of the LEDs.

Unfortunately in the process of replacing I must have strained one of the ribbon cables - I now have a line running down the side of the screen.
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Old 07-23-2019, 07:42 AM   #8
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Default Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

Good job on the fix. For future reference, can you please supply the part number or seller you purchased the LED strips from?
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Old 07-23-2019, 08:33 AM   #9
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Default Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

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Originally Posted by jetadm123 View Post
Good job on the fix. For future reference, can you please supply the part number or seller you purchased the LED strips from?
This is what I purchased - later on I realized that other sellers on AliExpress had it cheaper - about $11. Attached a picture for posterity.

This is the same panel used in the 27Ē iMacs- the backlight likes to fail there too, typically the connector on one side goes out, leaving half the display dim.
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Old 07-23-2019, 09:07 AM   #10
jetadm123
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Default Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

Thanks! I'm sure others with the same problem will appreciate this info.
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Old 07-23-2019, 07:52 PM   #11
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Default Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

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Originally Posted by jetadm123 View Post
Thanks! I'm sure others with the same problem will appreciate this info.
Hopefully. Other people with no backlight found that giving a constant 3.3v to the PWM input on the backlight controller restored the backlight - at full brightness, permanently of course. They seemed to think that the issue lay in a bad microcontroller that failed to produce the signal. Given the success of this repair, I'm inclined to think that the issue was in the overcurrent protection correctly triggering and the failure to generate the PWM signal was merely a symptom of aging backlight.
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