My 24in Apple Cinema Display dead now...

[Loa]

[Edit: See my last post]

Hello,

Been using my display since i got my mac pro in 2009, and now it won't turn on. The USB passthrough works, but it doesn't "light up". 15 minutes ago, it just flickered after powering up and never worked since.

If I force a parameter RAM reset, the display flickers on and off very quickly (screen is pure white), but doesn't work after that.

So I know that the LEDs are fine, but why then doesn't it work?

Loa

P.S. The GPU is fine, I tested it with my TV and it works. This is a PC HD6870, and the display is plugged there usually. I tried using my old GT120 (that is not usually used) but it doesn't work in that card either.

 

[Big-TDI-Guy]

With the computer and display on - hold a flashlight directly up to the display (right onto it - so you can't see any glare) - and see if the display functioning - but without a back light.

 

[hfg]

Does it work without the USB cable plugged into your computer?

 

[Loa]

Hello,

Yes it is working, but no backlight.

Strange thing is that I zapped the PRAM again, and the backlight did flicker on and off... So the backlight "can" work, but it just doesn't.

Loa

----------

It IS working wihtout the USB hub.

Restarting, trying again...

(there was a USB extension between the display and the Mac: testing it)

 

[Big-TDI-Guy]

If you can still see the display itself is working - but sans back light - you likely have a LED or LED Driver (power supply) problem.

It looks like the LED driver is integrated into the logic board itself. Not sure about the power supply for this board.

Logic Board: http://www.macpalace.com/661-4823-l...a-display-a1267-mb382ll/a-0171-2292-2695.html

Power Supply: http://www.macpalace.com/661-4821-power-supply-212-w.html

Hard to isolate the root cause without some electronic testing / troubleshooting.

Edit: FYI - I just found a picture of the 661-4821 power supply board on eBay, and I see stacks of electrolytic capacitors on it - having seen swollen caps on dozens of LCDs with the same failure mode as yours (although with CCFL instead of LED) - I'd suggest a google on "swollen caps" and/or "capacitor plague" - then if you're brave enough, open up your display, and see if you have any. It's usually very obvious if you have them - you can see it physically - no test equipment required...

 

[Loa]

Wel, it looks like it could be a simple extensions issue

After making it work with only the minidisplay port plugged in the 120GT, it worked normally. After plugging the usb cable, it worked normally. as well. If I plug the TV in the HD6870, it works as well. A few restarts later everything works well. At this point there are no extensions (there were two before: usb and mini display port). Even when I put both the display and the TV on the Hd6870, it works.

One of my extensions must be dead. Tying to figure which one.

Thanks for the help!

 

[Loa]

Hello,

Now I think it's really dead: when I was fiddling with the cables, it must have been in its dying throes.

Same symptoms: when I plug it in it flashes very very quickly 3 times in a row, then goes dark. The pixels themselves are there and working (using a flashlight to see), but the LEDs just don't stay on.

Any ideas?

Loa

 

[MacVidCards]

Do some googling with that model number and bad backlight. I had a PowerBook that burned out it's backlight tubes and another that burned up the inverter board.

Parts different on LED Zbut functions the same.

 

[Big-TDI-Guy]

If it's flashing on power-up 3 times and then cutting out - it sounds to me like a POST failure in your LED driver.

I'm guessing here - but upon power-up, either the LED power supply / driver is detecting a short, or an open - and after 3 attempts - powers off to protect itself.

Most LCDs (never worked on a 24" Cinema Display as of yet) - use multiple "channels" on the LEDs. So in a string of LEDs that provide the backlight - it's common to see 5 or more "strings" of LEDs. So if one of those sets has failed - it may not be immediately obvious on the screen, as the remaining sets still provide some light. But the driver reacts to the defective channel(s) and shuts down everything.

Take a drive down to NH, I'm willing / bored right now.

 

[Loa]

Hello,

Big TDI guy, I'm tempted to drive down there, it's not that far from here... but it's still a long day of driving.

I'm willing to get the suction cups and open the display: is there anything I could to myself?

Thanks

Loa

P.S. Here is a pic from the display as it is flickering (had the camera on a 1 second shutter, so all the flickerings are there). The first image is "as is" and the other one has been worked on in PS to increase contrast to show the worse image possible. (The blob in the lower middle of the image is the reflection of the camera, and the strange horizontal lines coming from the right side are reflections from wooden bows hung on my wall.)