Apple 27" Cinema Display (A1316) has trouble turning backlight on

[Misterkeeks]

I have an Apple A1316 27” 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 it's 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 it's on, it's 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.

[CapLeaker]

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.

[Misterkeeks]

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.

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.

[R_J]

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.

[CapLeaker]

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.

[Misterkeeks]

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.

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.

[Misterkeeks]

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.

[jetadm123]

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?

[Misterkeeks]

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?

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 27” iMacs- the backlight likes to fail there too, typically the connector on one side goes out, leaving half the display dim.

[jetadm123]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

Thanks! I'm sure others with the same problem will appreciate this info.

[Misterkeeks]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

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.

[Misterkeeks]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

I spoke too soon regarding the success of this repair. Shortly after replacing the LED strips, the problem persisted.

So,

• Replacing the Power Supply
• Replacing the LED Strips

both have failed to fix the issue, which leaves me with the logic board.



For what it's worth, 27" iMacs use the same panel, but do not fail in the same way. I guest that should suggest that the failure is not located in the panel, but in the logic board (which is not shared with the 27" iMac. Any ideas on how to troubleshoot this?

This problem happens when the backlight controller does not provide a PWM signal to the LED drivers for brightness. Previous "repairs" seem to simply bypass the controller and tie the PWM to 3.3v, thus keeping the backlight on at full brightness.

[Misterkeeks]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

Any thoughts before I spend $30 on a (used) logic board/backlight controller?

[CapLeaker]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

Personally, I’d stick it in my ultrasonic cleaner and after that I’d bake it in the oven for 20 mins. Got nothing much to loose.

[avneeshshrotria]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

guys I need the values of some of the components around NCP1605 on the power supply board .

I'm attaching an image for reference . I would really appreciate it if someone could help.

Apple thunderbolt display PSU

Board model number : PA-3251-3A


the first one I got the this thread itself.

and the burnt one is what is the current condition of my power supply .

Also if someone is aware of schematics . I could just use that.

thanks everyone. this is one of the best fourms I've come across .

[avneeshshrotria]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

Hey , can someone please help ?

[Misterkeeks]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

Hey , can someone please help ?

Do you still want this info? Let me know and I will look. Send me a PM or I will likely not see your post.

[avneeshshrotria]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

Thanks very much. Yes I’m still stuck with a non working display dude to this power supply issue! Please share images or values as you see fit !

[iuliantv]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

hello, I have this apple cinema display 27 "A1316, with well known problem, it has no backlight, I applied the method described in other forums, I minimized the light from the macbook, I restarted the systems, it started ok apple cinema display 27", the light seems to be correct, without shadows, spots or dimly lit parts, which leads me to think that the LEDs, the backlight is ok, I applied the method described on other forums, I removed the 3 resistors, and I applied 3v on the ends of 2 of them, I put on all 3 ends, without result, did anyone find another solution? something needs to be done besides removing the 3 resistors and applying 3v ,? thank you
https://www.ifixit.com/Answers/View/...he+Logic+board

[iuliantv]

Re: Apple 27" Cinema Display (A1316) has trouble turning backlight on

Thanks very much. Yes I'm still stuck with a non working display dude to this power supply issue! Please share images or values as you see fit !

I'm sorry, but my apple display 27 "has a completely different source of power, otherwise I would put pictures with it