Backlight LCD turns off + Buzzin Noise

Hi there,

my Apple Cinema Display 27" (no more warranty) got some problems with its backlight and I'm not quite sure whether its the logic board or the power supply..

It works for a few minutes, but than it randomly turns down the backlight of the LCD. There is still a picture, that can be seen e.g. at direct sunlight. So the LCD itself should work fine!

I can speed up this more or less random process by in- or decreasing the brightness.

If i disconnect the display from power and reconnect it, it works again for some minutes. Then, same procedure...

There is also a buzzing noise coming from "inside" which gets louder the brighter the LCD is but doesn't really stop when the backlight turned down again.

For me this buzzing noise sounds like a damaged transformer or some other power supply problems... but I'm not sure...

What I'm sure is, that these two problems have the same source and hopefully will have the same solution.

I already tried the things listed in the Apple Technician Guide and the ones on the internet...

What do you think? I thought I'll ask you for some advice befor ordering some parts like new power supply or new logicboard..

Thank you! :-)

Update

Alright guys... I replaced to PSU. Nothing changed..

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Had the same issue a month ago. Buzzing all the time and increasing the brightness made it worse.

Took it to the Apple Store and they replaced the psu for $129 Canadian. You have to make sure it's the new version of the power supply. Problem was fixed. No more buzzing.

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Hi Alex!!

Well... that looks like light at the end of the tunnel...

I ordered this part... do you know the part no?`

http://www.cdx.de/store/products/APPLE-E...

aaaaand.. can I use a thunderbolt display psu? this one should be newer?

thank you!!

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Yes the thunderbolt one should work without fail. The internals of the cinema display and the thunderbolt display are identical (with the exception of the three extra ports at the rear).

looking at my receipt from the apple store, the part that they provided was 661-6048. this cooresponds to the newer PSU.

I've read a lot of people have the same buzzing issue - to the point that I think it should be considered a defect and covered by apple. oh well. it's an easy fix.

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Hello! I have exactly the same problem, too,

when 100 brightness motherboard(!) buzzing

I disasambly montior, check the power supply 24 Volt, all ok

I replaced the motherboard and did not help, I think the problem is somewhere in LSD but where?

I do not know :(

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Mo Vaillant estará eternamente agradecido.
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