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Very Dim Thunderbolt Display?

cambookpro

cambookpro

macrumors 604
Original poster
Feb 3, 2010
7,234
3,382
United Kingdom
Hi,

I recently got my TBD back from Apple after they replaced the logic board. However, on Tuesday I noticed that it is very dim. It wasn't being like this last week.

I've attached a picture - both displays are on 100% brightness.

Bearing in mind that the Thunderbolt Display is actually meant to be much brighter than the MBP on paper.

Tried turning off/on - no luck. Looks like another trip to the Apple Store then!
Thought I'd quickly check with MR first though, they may have some pearls of wisdom I have missed out on :p

Thanks.
 

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I have 3 possible issues you may be experiencing here.

When they put your display back together, they might not have correctly aligned the ambient light sensor. Not sure where the sensor is located on your display - on my old iMac it's a small "eye" on the bottom. I'd guess it's near your camera on the current displays. Anyhow they tend to use a foam tape around the sensor - so light coming from inside your display - does not shine into the sensor. It's easy for this foam tape to roll over the sensor / block it when reassembled. So your display thinks the room is always dark - preventing 100% brightness. Never having used a thunderbolt display - not sure if there is an option to disable the ambient light sensor or not - but if you can, and it suddenly gets brighter - you've got your cause. Alternatively, you can shine a flashlight into the sensor area directly - see if this causes a jump in intensity. (it should)

The other option - most larger displays use multiple back lights - whether LED back lit or CCFL - it's possible they failed to reconnect one of them. New displays have such good diffusers / light blenders inside - it's very difficult to detect "banding" or intensity gradients across the display. However, if you see a difference in intensity on one side vs the other - it's possible you have a LED array that's out.

Finally - it could be a firmware / board rev change - maybe Apple switched LEDs / vendors where one requires more power than the other - however if this was an Apple store - I'd genuinely hope they wouldn't miss something like this.

I'd wager the ambient light sensor.
 
Big-TDI-Guy said:
I have 3 possible issues you may be experiencing here.

When they put your display back together, they might not have correctly aligned the ambient light sensor. Not sure where the sensor is located on your display - on my old iMac it's a small "eye" on the bottom. I'd guess it's near your camera on the current displays. Anyhow they tend to use a foam tape around the sensor - so light coming from inside your display - does not shine into the sensor. It's easy for this foam tape to roll over the sensor / block it when reassembled. So your display thinks the room is always dark - preventing 100% brightness. Never having used a thunderbolt display - not sure if there is an option to disable the ambient light sensor or not - but if you can, and it suddenly gets brighter - you've got your cause. Alternatively, you can shine a flashlight into the sensor area directly - see if this causes a jump in intensity. (it should)

The other option - most larger displays use multiple back lights - whether LED back lit or CCFL - it's possible they failed to reconnect one of them. New displays have such good diffusers / light blenders inside - it's very difficult to detect "banding" or intensity gradients across the display. However, if you see a difference in intensity on one side vs the other - it's possible you have a LED array that's out.

Finally - it could be a firmware / board rev change - maybe Apple switched LEDs / vendors where one requires more power than the other - however if this was an Apple store - I'd genuinely hope they wouldn't miss something like this.

I'd wager the ambient light sensor.
Click to expand...

I have this box unchecked in System Preferences, and shining a torch on the camera area unfortunately yielded no change.

From what I can tell, there is no change in shade throughout the display.

Thanks though - not sure how to check for the 3rd option?!
 

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Does the camera work correctly? Microphone?

I'm still leaning towards a blocked or unplugged ambient light sensor.

Not ruling out back light or main board driver - but I've seen enough sensors not aligned with the "window" and/or foam blocking their view - that I'd wager this is likely your problem.

Edit* With your ambient light sensor turned "on" set your display brightness to "low". Then try the flashlight aiming into the sensor, and watch for a change in intensity.
 
Try a few combinations of mirroring and not... while adjusting the brightness display.

My configuration is different than yours... but it does have an odd behavior that might be your issue. I have an iMac with an ATD as a secondary monitor.

If I have the displays NOT mirrored (my normal mode)... then the brightness keys only adjust the iMac display. If I have switch the displays to mirrored mode... then the same brightness keys only adjust the TBD.

Try adjusting with different configurations of display organization and mirroring (not airplay mirroring).

I hope they fix this with Mavericks.

/Jim
 
Same thing happened to mine, eventually Apple just replaced it with a new unit.

cambookpro said:
Hi,

I recently got my TBD back from Apple after they replaced the logic board. However, on Tuesday I noticed that it is very dim. It wasn't being like this last week.

I've attached a picture - both displays are on 100% brightness.

Bearing in mind that the Thunderbolt Display is actually meant to be much brighter than the MBP on paper.

Tried turning off/on - no luck. Looks like another trip to the Apple Store then!
Thought I'd quickly check with MR first though, they may have some pearls of wisdom I have missed out on :p

Thanks.
Click to expand...
 
Ok, thanks for all the replies. I will do everything mentioned to try and get it working, but if not, I scheduled a Genius Bar appointment for tomorrow.
 
Big-TDI-Guy said:
Does the camera work correctly? Microphone?

I'm still leaning towards a blocked or unplugged ambient light sensor.

Not ruling out back light or main board driver - but I've seen enough sensors not aligned with the "window" and/or foam blocking their view - that I'd wager this is likely your problem.

Edit* With your ambient light sensor turned "on" set your display brightness to "low". Then try the flashlight aiming into the sensor, and watch for a change in intensity.
Click to expand...

Camera and mic work fine. I just tried setting the brightness to low and ticking the automatically adjust box, and upon shining a torch at the camera area, it climbed all the way up to "maximum" brightness. I think that must mean the ALS is working?

flynz4 said:
Try a few combinations of mirroring and not... while adjusting the brightness display.

My configuration is different than yours... but it does have an odd behavior that might be your issue. I have an iMac with an ATD as a secondary monitor.

If I have the displays NOT mirrored (my normal mode)... then the brightness keys only adjust the iMac display. If I have switch the displays to mirrored mode... then the same brightness keys only adjust the TBD.

Try adjusting with different configurations of display organization and mirroring (not airplay mirroring).

I hope they fix this with Mavericks.

/Jim
Click to expand...

Thanks for the advice, but with my setup, the bulit-in keyboard has always adjusted the MBP display, and my external keyboard has always adjusted the TBD. I can turn the brightness up and down on both, just the TBD seems really dim at max brightness!

pcdsl said:
Same thing happened to mine, eventually Apple just replaced it with a new unit.
Click to expand...

Ok, thanks - fingers crossed then, hey!
 
So I turn it off and on just before my Genius Bar appointment -- it works absolutely perfectly.

I cancel the appointment.

I come back after lunch, and it's completely dead. Won't turn on at all, bearing in mind this was the problem that Apple were meant to sort out a couple of weeks ago.

Going in tomorrow, and they better offer some damn good service or I will be apoplectic. Not happy at all :mad:
 
Super unfortunate. I sure hope they offer you a new one or something, all these appointments and re-occurring problems should deserve a new one.
 
Well, went in today and it actually reminded me why I buy so many things from Apple :p

I have to say that they were very, very reasonable. I couldn't reproduce the fault and it started working perfectly, but they saw how many notes were attached to the serial number and offered me a brand new unit.

Very happy, works perfectly now.
 
cambookpro said:
Well, went in today and it actually reminded me why I buy so many things from Apple :p

I have to say that they were very, very reasonable. I couldn't reproduce the fault and it started working perfectly, but they saw how many notes were attached to the serial number and offered me a brand new unit.

Very happy, works perfectly now.
Click to expand...

That's wonderful. How long have you had that other TBD before they replaced it today?
 
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