iMac buzzing noise when screen dims

Thanks Barry. Logically I thought it was wrong, as my MacBook doesn't do it, but I don't know if the screen technology is similar enough to be a fair comparison.

When the Macbook is ready for collection I'll book an appointment with a Genius and take the iMac along.

Hi All and thanks for your replies.

Had a call from the Apple store last night to say my MacBook is ready for collection, so thought I'd make an appointment online to bring the iMac in. Before I made the appointment, I listened for the buzzing noise, to make sure it was still there.

It wasn't!!!

I dimmed the screen all the way down..and up...and down loads of times, and NO noise at all! The only noise I could hear was from an internal fan inside the casing, which is constant and no variations of sound at all.

I leave the machine on all the time (UPS connected!) and set the display to turn off after 15 minutes, so I wondered if it was because it was warm (well, the display hadn't been on for long, but rest of machine would've been warm), so turned the machine off overnight and tested this morning...again, silent! I even tested with Safari filling the whole screen on the apple home page, which is predominantly white (and bright).

So for now, it seems to be ok. The only other test is to try it after the display has been on for a while (say 2 hours?), to ensure the display is fully warmed up, which I will try soon.

It definately used to make a noise, so I wonder if it has just settled down, and for want of a better phrase, burnt in? (as opposed to burnt out!!!).

Thanks again and I'll keep an eye (ear) on it!

Kevin

Bummer...

iMac was in use last night for a while, so the screen was warm and it made the noise.

This morning, after the screen had been left off all night, there was no noise.

So I set the properties to leave the display on (with a screensaver) and went and watched the Royal Wedding...just came back and tested.

With the screen at full brightness, the only noise is the fan and perhaps a very,very,very slight high pitched noise.

However, turning the display to its lowest brightness setting via the keyboard, you can clearly hear a buzzing noise, so it appears the issue is only present when the screen has had chance to warm up.

So just about to book a genius appointment and take it in!

Managed to book a genius appointment today so visited to collect my repaired MacBook and to take my iMac in for investigation.

Showed the guys this thread....apparently this model of iMac doesn't have an LCD Inverter, but they have seen this issue before and suspect it is something called the LED Backlight Board, which controls the power to the LED's and thus the brightness (I guess it is the equivalent of the LCD Inverter).

As the problem only appears to be present when the machine/screen is warm, there was no point trying to demo it in store, so they have booked it in for investigation/repair and will call me when it is ready.

On a slightly different point, the guy that served me today was brilliant! His name was James and he was really polite and helpful, just what you want!

So, I had the call from Apple Store to say the iMac was repaired. I asked the guy if he had heard the original problem and he said yes and that it was now quiet.

So on Saturday I went to the Apple Store (100 mile round trip). Collected the iMac and took it home.

Unpacked it and put it on my desk. I could immediately see marks on the screen, which at first looked like dust/dirt on the glass, so I found a microfibre cloth and gave it a wipe....no difference....the marks are under the glass!

I wasn't impressed, as looking closer I could also see a fingerprint...again, behind the glass!!! On the back of the iMac there was a tiny (pinprick size) mark in the aluminium casing! Not worried about that cos its tiny, but the screen issue is annoying.

So I rang the store and they said to bring it back in. I pointed out the distance but they said there was nothing else they could do apart from have me dismantle the machine to clean the glass - I did not want to do this as it is in warranty. Booked it in for the following morning.

Left it on overnight to test the original buzzing noise and guess what....it is still there!!!

So, to recap - they had my iMac in to repair a buzzing noise when the screen was dimmed and the machine was warm. They replaced a part. They havent cured the problem and in the process have left fingerprints/dirt on the display, under the glass.

Not what I would call very good at this point!

So I took it back on Sunday morning hoping the guy would clean the screen but they were short staffed and busy so he didn't have time. Not really a problem as it needs to stay in for more investigation on the buzzing.

The guy was apologetic and did seem concerned that the buzzing hadnt been fixed. So the machine was booked in with possible replacement of the LED Backlight Board (again!) and possible glass replacement if needed, which they will assess when they dismantle it.

As long as its resolved successfully then I'm ok, but not impressed with the workmanship at this point for it to be returned in that state. Obviously, if I'd checked it instore on collection I would've spotted the marks, but as the original fault only happens when warm, there was no point, and I assumed the screen would be no problem!

Ouch, thats not what I wanted to hear!

I had a call today to say it had been repaired - this time they have replaced the PSU and the tech (sorry, Genius!) assures me that the machine was on all afternoon and when he checked it by lowering the brightness he cannot hear any buzzing. My power settings were set to leave the machine on, not turn the screen off, but use a screen saver (normally turn the screen off after 15 min, but set to this for testing) so assuming it was logged into my account (they have my password) then it will have been warmed up. Only time will tell, but he reckons he turned the aircon off in the room and put his ear by the screen...when I did that previously it was clearly buzzing, so will see...

Asked about the marks behind the glass and he didn't know what I meant! He said to check it when I collect it (dont worry, I will!!!) but I said that as its such a journey could he double check now....he said the screen was clean, so again, will see this weekend when I collect it!

So I collected my iMac yesterday from the Apple Store. I checked for dust and marks before leaving the store, and there were several dust particles and one big mark behind the glasss. The guy took it out the back and bought it back 5 minutes later and all but 1 bit of dust were gone, so I took it. Why cant they get that bit right first time?

Got it home and powered up. Left it for a few hours and tested for the buzzing by lowering the brightness.

STILL THERE!!!!

So my conclusion is that all the techs in the Apple store are deaf, as on both occasions, they have told me they can't hear anything, but in the right conditions (i.e. warm screen and dim settings) the noise is definately present.

I'm so not impressed with this. Not so much the buzzing noise, as a previous poster said others do it, so I will just live with that and assume it is in fact, normal behaviour. They've replaced the PSU and LED control board...I guess, if it is a hardware fault, then the only other thing it could be is the actual panel itself, but other than the noise, the panel is fine, so I'm not going to risk that. What I'm not impressed with, on this repair, is the way the machine was handed back the 1st time, with definate marks on the panel and a fingerprint, and then on the 2nd collection, still more dust. And on both attempts, the tech has assured me on the phone that he witnessed the buzzing noise before the rapair and that it had definately gone after the part was replaced!

I recently had my Macbook Pro in for a replacement logic board, and although it was completed in 1 visit, when I collected it and turned it on in store, it was still in some diagnostic mode (black screen with white text) and they had to do a key combination to sort it (a simple fix, but the tech had to ask his colleague!). Again, not the way to hand a machine back!

I work in IT for the NHS and when I have a PC in for repair, I ensure that my fix works, and it is handed back clean. Unless the problem is intermittent (which my buzzing noise isn't!) then you can easily test if it is cured. Handing the machine back in a dirty state doesn't give the user/owner much confidence in the quality of the repair, and makes them think the machine hasn't been looked after. I don't want my £2000 iMac being looked after by some retard that doesn't give a ****!

Hi Whagi,

Thanks for your post. Thats exactly my point and frustration - Apple products are not cheap, and therefore when taking them for service work you want to know they've been looked after, especially at an Apple Store! Dont get me wrong, the guy may have used the utmost of care in his work, but when it comes back to me with marks/fingerprints/lots of dust behind the glass, then it doesn't give a good impression. I've read posts saying that the dust is unavoidable, but the amount that was in it the first time was ridiculous, and there is no way they wouldn't have known it was there.

I only took it in due to the buzzing noise which I have lived with since new - I only did it now as my Macbook recently needed a new logic board, so kinda thought I'd get the imac done as well. As it turns out, I'm no better off now - the buzzing is still present. Can I ask if yours does it? When you've been using it for an hour or two (i.e. the screen has been on constantly), if you press the F1 key to make the screen dim, as it gets dimmer and dimmer, does it make a buzzing/humming noise? Then when pressing F2 to make it bright again, does the noise go?

I've decided I'm gonna ignore it now. Admittedly, its not something I do anyway, but its one of those things, once I knew it was there, it bugged me, which is why I thought I ought to get it fixed.