iMac buzzing noise when screen dims

I'm happy that your's is ok!...and jealous!!!

It proves that they dont "all" do it!

My dilema is, if I take it back, they might refuse to do anything, as they seem to think it is fixed! They might change the screen, but then I might get other problems, such as dead pixels etc, while at the moment I have none. They might put more scratches/dents in the alu body.

Considering the LED backlight board and also main psu has been replaced, could it be the actual panel? I assume the actual LED backlights are part of the main panel, so could that be at fault?

Does anyone know of this happening and actually being repaired?

So after my last post I searched again online for this, and found more forums saying it does/doesn't happen. Thought I cant be doing another 100 trip to the apple store (well, 200 mile by the time I've delivered it, then collected it a week later) so I phoned Applecare directly.

They have advised me to try an SMC reset tonight, but have arranged for it to be collected from my place of work tomorrow by an apple authorised repair company, for them to look at it. If the SMC reset cures it (a long shot) I can cancel the collection.

Will await the outcome of this approach!

Hi urartu,

Not yet. It's been into the Apple store on 2 occasions. The first time they replaced the LED Board and the 2nd time they replaced the main power supply unit (psu). These made no difference.

At that point I was going to leave it, thinking it must be normal, but found several internet forums where people said they had it (like you!) and others said they didn't have it. Some said they had it fixed, and the most common cure seems to be changing the psu!

So I decided to ring Applecare, instead of just taking it to the apple store. I explained things to them and they arranged to have it collected by an apple authorised repairer, for them to try.

The Applecare guy asked me to do an smc reset (remove power lead, then hold power button for 5 seconds) but this made no difference.

My iMac was collected on Tuesday and I phoned the company yesterday to confirm they had received it! They guy I spoke to told me they had the machine and had tested it, and confirmed the buzzing noise. They have ordered a new LED board and a new PSU to fit, but they are awaiting delivery of those.

When I told him the Apple store had already replaced those parts, he was surprised, but did say he had a similar one recently where he had to change the LED board more than once!

So I am now waiting for them to get the parts and fit them, then test it and when it is fixed they will ring to arrange return.

They reckon they will get the parts on Monday. When I get it back I will post here the result.

I was pleased that they actually confirmed the noise though, as at least now they definately have something to listen for when the parts are replaced.

I found this youtube video which is exactly my problem (and spec and age of my machine!)

http://www.youtube.com/watch?v=0CECWAUmGaE

Hope this helps. If you have Applecare or in warranty, I'd get it looked at, cos although I have brightness set high, so dont hear it that often, I know its there and am worried it might get worse over time.

Edit : Forgot to add, it only seems to happen when its warm. If the machine has been off all night, it doesn't buzz, but after about an hour of use, it will buzz. Also, some of the forums implied that US machines dont do it, only european and UK etc, which does point more to higher voltage.

Arh, yours is a slightly different issue to mine. Mine doesn't do it when cold, and it is a definate buzzing noise, not a high pitch noise (I get a slight high pitch noise on full brightness, but only heard that when I had my ear against the display to test for the buzz).

Before all this, the imac hasn't had any work, so it was all original until a few weeks ago. Now it is on its 2nd LED board and 2nd PSU and currently awaiting them to fit a 3rd led board and 3rd psu.

Umm...the link would be useful, never come across that.

When I say warm, I mean the display. If I leave the computer running, but let the display go to sleep, and leave overnight, the noise doesn't happen, even though the "computer" will be warm, but the display isn't. If I then turn the display on, and say, screen saver, so the display gets warm, then it will happen. Admittedly though, overnight the cpu will not be working.

So had a call from the repair company to say my iMac is repaired and has passed all there tests. They are sending it back and I should have it tomorrow...

Will wait and see!!!

Hi All,

Well, I had a crap day yesterday (got called to the hospital at 2AM as my father in law who has been in hospital for 2 weeks took a turn for the worst) so I didn't goto work yesterday, but spoke to a colleague who confirmed the iMac had been delivered.

So when I left the hospital last night, I went via the office to collect the iMac.

Got it home and set it up. Turned it on and just got a white screen...no "Bong" or bootup etc. Checked Google and found out how to reset nvram etc, so did that and it booted ok.

All seems ok, case not damaged, screen clean etc.

Dimmed screen and no noise, but wasn't expecting anything as still cold.

So left it for a couple of hours with just the screen saver going and then tested....

QUIET!!!!

Was really knackered, so turned it off again and went to bed! but the initial result looks like its solved, as previously it would definately make the noise at this point!

The letter that accompanied the machine said the fault had been resolved by "replacing the power supply and backlight board" - this is what the Apple store did, so perhaps the replacements that the apple store used were also faulty?

Anyway, the company that did the repair (it was all arranged through AppleCare) were called Amsys, and their website is www.amsys.co.uk

I'll keep an eye on it over the next few days and do more tests and will report back, but at this stage I'm inclined to say its fixed!

So I've let the iMac warm up and cool down several times now, and each time that I dim the screen using the keyboard keys, or put the display to sleep (by setting the top left corner as a hotspot) the buzzing noise is not present, even though it is thoroughly warmed up.

So it seems that the buzzing noise is a definate hardware fault, caused by either the LED backlight board, or the PSU (cant say which as both have been changed).

Time will tell if it is a longterm solution, or if the components will "degrade" and the buzz return....but it definately isn't buzzing anymore!

Hi,

Wow, was it back in May that all that happened, seems ages ago!

ok, so has the problem happened again? No, my iMac is still quiet when the screen dims etc.

Can't comment on new iMacs, but remember not everyone ever had this issue.

Good luck with whatever you decide to purchase.