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Hello,
I have a 2009 27” iMac that upon pressing the power button, makes the Mac chime, but then displays nothing on the screen and the fans then spin up. I have tried resetting the SMC and checked for other power related issues.
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Using a flashlight, place it on the display glass at a sharp angle do you see a faint image of your desktop and the icons? You could also try an external display as well.
If you see the faint image and/or external shows a good image. Your internal displays back light needs repairs. A common issue is a burnt LED Driver board iMac Intel 27" EMC 2309 and 2374 LED Driver Board Replacement and here’s the needed part iMac 27" LED Driver Board (‘09) 661-5311 for reference.
If you look at the far bottom left of the logic board you should see a piece of black electrical tape covering the logic board
You’ll see four onboard diagnostics LED’s
With the display disconnected what do you see when you power the system and hit the power button normally.
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I do not see any image when doing this, thank you though
Not good! Can you give an external monitor a try? Do you see an image that way?
If you can't do that are you able to see a FireWire icon on your screen when you startup your system in Target Disk Mode? Restart your system and press the T key
Reference: Mac startup key combinations
@danj I'll try this as soon as I can, I had to go out of town due to work this weekend, but as soon as Monday I will be able to try these two.
@danj I hooked up an external monitor, it also displays no output at all
@tenter02 - Did Target Disk Mode show you an icon on the screen?
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This behavior isn’t easily diagnosable with the symptoms described. Have you tried reset the PRAM?
See here:
https://support.apple.com/en-us/HT204063
If this doesn’t correct the behavior you may have a hardware issue. When you say that the fans “spin up” do you mean that they spin at a higher rate than normal? In 2009 the thermal sensors for component temperatures were replaceable, can go bad and cause disengagement of components and high fan RPMs.
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I've tried resetting the PRAM and SMC. When I say the fans spin up, I mean they go full speed.
That's a bummer, this is unlikely to be solved without a takeapart as described by @danj above.
The fact that it doesn't output to an external monitor indicates a graphics failure of some kind. When you powered on and hooked to an external, did you give it enough time to boot to the desktop? Sometimes these older models will not output to an external until about midway through the boot cycle.
When I get to this point and want to be sure it's trying to boot without any output to the monitor, I'll power it on, then hook up the external display, and put an ear to the center of the unit listening for the hard drive working.
If you don't hear a pretty busy-sounding series of rapid clicks, it's not trying to boot to the OS.
If it's not trying to boot to the OS, power down, power back on and hold down the "alt" key for about 10 seconds.
Even through you won't be able to see which volume you're selecting, press the enter button to select whichever unseen volume may be on the boot screen.
@seymourglass I've let it run for about 30 minutes once, just see if there is something maybe taking a while, but nothing came on the screen.
I can hear the hard drive working, and based off of what @danj said, I think there is an issue with the graphics card.
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3 Comments
Try checking your connections to the moniter. If the problem still persists then your moniter could possibly be damaged.
by John Rochford
@johnrochford familiarize yourself with the device that you are giving answers to. Your answer was not related to the device in question
by oldturkey03
@oldturkey03 If there is nothing on the screen then maybe the moniter is not connected correctly and the fans would likley spin up if the device was trying to update. Just a thought
by John Rochford