モデル番号A1312 / Mid 2010 / 3.2 GHz Core i3もしくは2.8 & 3.6 GHz Core i5もしくは2.93 GHz Core i7, ID iMac11,3

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iMac 27" 2010 Chime loop and black screen issue

After system update (High Sierra) I get a black screen and the start up chime continuously loops. Keyboard commands do not work neither does putting in an OS X disk as the disk drive.

I also tried to plug in an external display (MacBook) using a Mini Display Port to Thunderbolt cable and I've got no signal.

Removed all RAM (4x2GB) got error beeps, put 2 back on and got the chime loop with the black screen.

Diagnostics LEDs: #1 is always on, #2 and #3 are on when the iMac is started, #4 is off.

What could be the cause of this issue? The computer has been working perfectly until now.

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Your MacBook won't work as an external display. You can hook it up via the Fireport and try to access the iMac's hard drive using Target mode. But my bet would be on a failed GPU. It will probably need to be replaced. I have also had about a 70% success rate with doing a hot air workstation reflow.

iMacのIntel 27インチ(Late 2009/Mid 2010) のグラフィックボード


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Hi Mayer. I'm having this exact same issue, same iMac model. None of the startup commands work. Just black screen and endless chime.

After doing some research, I decided to open the iMac to check the 4 LED's on the logic board, just to find out that on this specific model, the 4 LED's would also be visible from the outside (bottom) haha.

However - all 4 LEDs are on, solid and not flashing. This leads me to the assumption that the Logic Board could be broken?

The iMac was working like a charm, and then, i was just checking my emails, the screen just went into some kind of grey pattern - I had to force shut it.

When I tried turning it on again, the chime loop set in. In a first try, I was able to boot it in safe mode holding down the shift key, where I got to the login screen, before the exact same thing happened again. After that - Booting the machine was not possible anymore (as described above). None of the boot up key commands work.


I know this is years later, but I have a 27" iMac 2010 that's doing the same thing - chime loop at startup, no fans etc as it's stuck in the chime loop that chimes about every 2 or 3 seconds, LED 1-3 are on, LED 4 off. Did you find out what the issue was?



@alrazule - I ended up fixing it by baking the GPU and that fixed it for now. A longer term fix will be to replace the GPU but as it’s already 10 years old I’m not sure it’s worth the investment. I did follow along a thread about replacing with a modern GPU so that it can run Catalina but again I’m not sure that’s worth the investment. If you’re interested in this route the thread has a wealth of information:


Good luck with your iMac!


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Hi both;

I ran out of options, so I decided to bake the Graphics Card - And this did the trick.

The iMac has been running flawlessly for another 2 years since it happened.


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Hi @fourcandles ,

I have the same issue, same LEDs as you. (4th is off).

The only way I get something different is

1) Remove ram which gives me the RAM error code


2) Removing GPU, which causes it to only have first two LEDs on as expected. Fans spin to mac but no sounds at all.

Other things I tried:

Recovery mode, safe mode, diagnostic boot, usb boot, new RAM sticks, no hdd, hdd with preloaded OS, replacing the CR3202 battery, reseated the CPU and GPU (also reapplied thermal paste since I was already in there). All these had no effect.

I am trying 2 things next unless you figured out the problem:

A) Tonight, 2020-09-17, try external display with and w/o GPU, his is very likely not the issue but just want to cross it off

None worked. Same Chime loop

B) Tonight, 2020-09-17, test LCD panel and lvds with an adapter board. This is very likely not the issue but just want to cross it off

My adapter was for the 21.5” model >.< Didn’t have the right power connector

C) Tomorrow, 2020-09-18, oven bake the GPU since I'm pretty much out of options.

If none work, I'll just gut it, toss a Raspberry pi in there with the LCD board and if it recognizes panel, use it for retro games or maybe just as an external monitor for my P

I don’t know why I didnt find this other post before:

Reviving iMac 2010 with looping chime on booting, VIDEOcard was faulty

He had the SAME observations as us. He replaced it the inferior card from the i3/21” model and it booted. Given this, have high hopes for tomorrow as I’ve read it fixes GPU issues although not as precise/efficient as hot flow but I don’t have a station and at my job there are plenty of ovens we use that aren’t used for food so I feel OK baking electronics in there. If it doesn’t work still, I’ll hunt for a cheap card (hopefully under $30), if it works, I’ll upgrade it to a gtx 765m or 770m which are reportedly better/less prone to failure and keep the cheapo as backup or for lending it to people local to me to troubleshoot their own iMac.


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@fourfourcandles and @virv , Thanks! Yeah, I baked the card yesterday and it worked! Such a simple fix.

Yeah, what I’m going to end up doing now that its operational is

A) replace HDD with an ssd to improve performance and reduce heat generation (the ssd cost should be a wash since if i move to a new system I can always take the SSD with me)

B) remove ODD and set the ODD fan to be controlled by GPU temperature (no cost)

C) Upgrade the i5 to an i7 870 which go for about $30 nowadays

D) See if I can find an Nvidia card 765M or above for under $100 and possibly sell this card for parts for $30 (with full disclosure) since I see nonworking ones going for $40. This way the upgrade to the more stable gpu/powerful will hopefully be $70. Least priority since I’m hoping if it lasts a few more years then the mxm card will go down.




in the meantime, i upgraded my 2010 27” iMac with a Nvidia GTX780M and successfully got Catalina to work on it (not easy, many sleepless nights, but well worth it!). Worked seemlessly for months!

Now - only 8 months later - it looks like that 780M is broken. Computer crashing, and back in Chime Loop I am :-(

Probably going to try and bake this card as well. Any other suggestions?


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niko さん、ありがとうございました!

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