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27" Cinema Display and Tzzzz sound

L

Lykos1986

macrumors member
Original poster
Jul 4, 2010
73
0
Hello to everyone!

I am facing a problem with my new 27” Cinema Display. It seams that there is a tzzzzz sound, produced from the screen.

The sound is constant and I can control it by changing the LED brightness. For example the sound is really weak at 65% of brightness. It goes to full volume at around 80% and again to a really weak sound at 98%. Outside these levels (from around 65% to 98% of LED brightness) the display is totally quite! No, tzzzzz sound or anything else!

I can hear the sound mainly from the bottom and top right part of the display. It seams that the other part of the display is always quite at all brightness’s levels. I am guessing that in this part is and the logic board that probably creates the noise.

The sound even in the highest peaks in not too loud at all, but the constant tzzzzzz is the thing that makes it really annoying. Sometimes that the rooms is totally quite I cannot even focus to my work! If there is sound in the room you can’t hear it.

What I suppose to do? Do I have a problem with the display or it is a common thing in all the new cinema displays? Do I have to call Apple for a display replacement? Any suggestions? Anyone with a 27” Cinema Display can here the same effect?

Thanks for your time… I will really appreciate and answer.


Otherwise I am really amazed from the display! Really bright, very good speakers (considering that is a display), nice dimensions and amazing design and picture!!!
 
I have a wireless router that makes a sound similar to this. It is very distracting. I looked into it and from what I could find it was a loose piece inside. Something you could solder together but its not worth the trouble. Easier to buy a new one.

In your case I would talk to applecare about it. It's not something that you will want put up with all the time. You shouldn't have to really. Also if something is loose it may break down the road. Unlikely I'm assuming, but still possible.

If its brand new they may call it DOA and you can just get a replacement.

tl;dr
I doubt this is something you will be able to fix yourself. Try to get a replacement.
 
What you're hearing is the LED brightness control circuit. LEDs are either on or off, and the brightness is controlled by switching them on and off at a high frequency, usually in the high audio range, with the observed brightness varying with the on to off ratio. At the highest brightness levels the LEDs are mainly on, so the buzz is reduced. It's the same for the lowest brightness levels where they're mainly off. The mid brightness range produces the highest sound levels.

The buzz is a known complaint with LED monitors and some laptops. CCFL backlight lamp brightness controls can also produce a buzz. One source of the sound is the ferrite torroid coils in the brightness circuit. The changing magnetic fields cause the windings to vibrate, depending on how tightly they are wound and sealed. Switching power supplies can produce similar sounds, which vary according to the load. The hollow aluminum case of the ACD makes a perfect sounding board for this buzz. There have been complaints of iMacs also producing a buzz.

This is usually most annoying to people with good sensitive hearing in the upper audio frequencies.

If you exchange the ACD, you may get one without the sound, but then it might have other issues. It's really a lottery.
 
drambuie said:
This is usually most annoying to people with good sensitive hearing in the upper audio frequencies.
Click to expand...

Maybe this is true. My sister can’t hear the sound from distance. She must put her ear exactly at the display to hear it and still she is saying that is really weak.

I can hear the sound from almost a meter away!

I’ve called Apple support and they told me that they don’t have any know issue about that buzzing noise problem, but they told me that I can bring my display to a genius bar in my local Apple Store. If they hear the noise then they will offer me a fix, not a replacement.

But since the Apple Stores are always crowded with people it is impossible to hear the noise! Somehow I must prove that I am not crazy!
 
Hehe! No, I am not shortsighted at all! Trust me; I am flying ultra light aircrafts as a hobby!

I am watching the screen from 1.5 to 2m away. Yeah, some will say that it is still too close but my office is really small as well.
 
Last edited:
Amazing! No I have and sound problems...

I am going to the genius bar this afternoon!
 
Lykos1986 said:
Amazing! No I have and sound problems...

I am going to the genius bar this afternoon!
Click to expand...

Sorry to wake this thread up but I'm so interested in knowing what they told you.

I have a similar -if not almost exact- issue. When the room is completely quiet I can hear that Tzzzz noise. It's pretty high (in frequency I mean) and behaves like this:

Brightness at 100%: No noise at all.
Brightness < 60%: Noise starts.

It's stronger as the brightness goes down and it hits its max when I turn the screen off (S.hift+Control+Eject).

The noise goes away as soon as the computer goes to sleep.

What did they tell you? Because I'm also afraid I won't be able to make them hear it in an Apple Store...
 
I've never heard mine -
but the sound described matches what usually happens in Light Dimmers.
They too get noisy as the output level is reduced.

Might have better results using a grounded outlet.
 
Last edited:
Philscbx said:
Might have better results using a grounded outlet.
Click to expand...

I am using one. :(

Want to add that it only suffers from this is the computer is awake. Doesn't need to be turned off, it can be in sleep mode and the sound goes away. If the screen is off but the Mini is awake doing something, sound appears.
 
Philscbx said:
I've never heard mine -
but the sound described matches what usually happens in Light Dimmers.
They too get noisy as the output level is reduced.

Might have better results using a grounded outlet.
Click to expand...

Just realized the Mini isn't actually using a grounded plug. Mmm… will try to find a grounded cable as the power connector seems pretty standard!
 
Philscbx -
Might have better results using a grounded outlet.
dasx said:
Just realized the Mini isn't actually using a grounded plug. Mmm… will try to find a grounded cable as the power connector seems pretty standard!
Click to expand...
If by chance a decent UPS is used - it can condition the A/C smoother.
I'll guess power there is 220v / 50 Hz, and while I was there - I could feel bleed through of the 50Hz to the surface of my MBP on ungrounded -
If lightly touched on the aluminum.

I noticed it from Germany to Sweden.

It's the only time I felt this - while over there -
It was never noticed here on 120v / 60 Hz in the US.

I didn't have a chance to test a UPS to actually test the bleed if conditioned power eliminated the effect.
Just speculation.

One might want to examine the circuit used for solid fit of plugs - and the specs of the circuit from panel.
Fuzzy Electrons get angry.
 
Philscbx said:
Philscbx -
Might have better results using a grounded outlet.
If by chance a decent UPS is used - it can condition the A/C smoother.
I'll guess power there is 220v / 50 Hz, and while I was there - I could feel bleed through of the 50Hz to the surface of my MBP on ungrounded -
If lightly touched on the aluminum.

I noticed it from Germany to Sweden.

It's the only time I felt this - while over there -
It was never noticed here on 120v / 60 Hz in the US.

I didn't have a chance to test a UPS to actually test the bleed if conditioned power eliminated the effect.
Just speculation.

One might want to examine the circuit used for solid fit of plugs - and the specs of the circuit from panel.
Fuzzy Electrons get angry.
Click to expand...

It does actually happen with the Mini too. And my iPad. Also with the iPhone. If you slightly rub any aluminum part, you notice it.

Called our home technician and he told me there are no grounded EIC C7. :(

UPS huh? Might try that, although good ones are quite expensive. :/
 
Thanks for the EIC C7 Code.
Hadn't noticed before.
images

Hard to believe no grounded circuits - as in 3 contacts in the wall.
Usually the Euro ground is the 3rd contact at edge of male plug where the shell is full circle pinch fit into outlet.
images

Maybe it's different in your location.

I suspect there is a power strip being used regardless - similar in design.
There are higher grade power strips that might deal with issue.
 
Philscbx said:
Hard to believe no grounded circuits - as in 3 contacts in the wall.
Usually the Euro ground is the 3rd contact at edge of male plug where the shell is full circle pinch fit into outlet.

Maybe it's different in your location.
Click to expand...

Asked him. Apparently these cords don't have a 3rd channel, (they lack of phase I think that he told me) that's why it probably wouldn't even make sense to make a grounded IEC C7.

I have now to decide whether I wanna buy a UPS or not. (I'm leaning towards the no, though)

Thanks for all your inputs!
 
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