iMac late 2011 Screen Issue

[sjsteve33171]

Hi All,

I'm a PC tech by day and recently a friend gave me his old iMac and said the screen keeps going off. If you can fix it you can keep it and he brought a new one. So I started looking at it. It's had several faults, all which I've slowly fixed and still no further in resolving the issue, so I'm now seeking any assistance please!

Firstly the CPU fan was dead according to the hardware diagnostics. I've replaced this now.
Graphics card has been reflowed and had new thermal paste applied.
Screen cable was slightly damaged so have replaced this.
Could see a capacitor had blown on the Inverter board. Have replaced this today.
SMC and NVRAM reset.

Still when I turn the mac on, its on for a few seconds before it goes black and there are no backlights. However, if I shine a torch on the screen, the screen does work as I can read what's on it. I also have a remote access tool on it and can access the mac remotely and it works still, but the screen has no backlights. Really I'm now stuck as to what the issue is. Hardware tests are passing, screen is working, just no backlights. Inverter board has been replaced with a working one, still goes off.

Has anyone else had this issue and can help or anyone may be able to tell me of any other tests I can do please? It's the only iMac in the house so I can't swap parts to test things either.

Thanks in advance!

 

[chscag]

Welcome to our forums:

Model and year of the iMac? If you can't find that info, jot down the serial number and go to the following site and enter the number:

Lookup Mac Specs By Serial Number, Order, Model & EMC Number, Model ID @ EveryMac.com

The reason we need the year and model of the iMac is so we can determine if the backlight is the older type or the newer LED type.

Also, there is a fuse on the logic board of some iMacs that protect the backlight. You may be able to find it by going to:

iFixit: The Free Repair Manual

You might also be able to get help from that site to troubleshoot the backlight problem. On the older Mac computers which used a fluorescent backlight, the backlight is encased within the display assembly itself. Apple recommends changing the entire display rather than just the backlight.

Good luck with the repair.

 

[sjsteve33171]

Welcome to our forums:

Model and year of the iMac? If you can't find that info, jot down the serial number and go to the following site and enter the number:

Lookup Mac Specs By Serial Number, Order, Model & EMC Number, Model ID @ EveryMac.com

The reason we need the year and model of the iMac is so we can determine if the backlight is the older type or the newer LED type.

Also, there is a fuse on the logic board of some iMacs that protect the backlight. You may be able to find it by going to:

iFixit: The Free Repair Manual

You might also be able to get help from that site to troubleshoot the backlight problem. On the older Mac computers which used a fluorescent backlight, the backlight is encased within the display assembly itself. Apple recommends changing the entire display rather than just the backlight.

Good luck with the repair.

Hi chscag,

Thanks for replying. I entered my serial and it says:

Family Mid-2011
ModelA1312 (EMC 2429)

Screen was going to be my next guess but was hoping to avoid that and hoped it’s something else.

Would be interested to know the type of LES Backlight if you know it?

Thank You


Sent from my iPhone using Mac-Forums

 

[chscag]

The display itself is okay since you can shine a flashlight and see video. If the backlight gives out that effectively gives you a dark screen with video.

You need to lookup your Mid 2011 iMac at iFixit: The Free Repair Manual and see what kind of backlight it uses. I suspect though on that model it's LED which could mean the board that controls the backlight may be defective. As stated previously, it may be easier to just change out the entire display assembly.

My lookup specs show that your iMac is a 27" model which means a new display assembly is probably going to be expensive. You might want to check eBay to see what they're going for but if you think you can repair the backlight without spending too much money, that's what I would do.

That particular model is obsolete according to Apple which means no parts or help from them is available.

Instructions for repair with pictures and step by step are available at iFixit: The Free Repair Manual.

 

[sjsteve33171]

The display itself is okay since you can shine a flashlight and see video. If the backlight gives out that effectively gives you a dark screen with video.

You need to lookup your Mid 2011 iMac at iFixit: The Free Repair Manual and see what kind of backlight it uses. I suspect though on that model it's LED which could mean the board that controls the backlight may be defective. As stated previously, it may be easier to just change out the entire display assembly.

My lookup specs show that your iMac is a 27" model which means a new display assembly is probably going to be expensive. You might want to check eBay to see what they're going for but if you think you can repair the backlight without spending too much money, that's what I would do.

That particular model is obsolete according to Apple which means no parts or help from them is available.

Instructions for repair with pictures and step by step are available at iFixit: The Free Repair Manual.

Hi Chscag,

Thank you for those pointers. I put a multimeter on the worlds tiniest fuse and it hadn’t gone it was fine. So I can only assume it’s the screen. I found a very good youtube video that pointed me to a common problem with a solder connector on one of the screen cables.

I’ve sorted both sides out to be sure and pieces it back together. So far it’s been running around an hour and hasn’t gone off. So fingers crossed you were correct with the screen diagnosis.

Thank You again!

Sent from my iPhone using Mac-Forums

 

[chscag]

Thanks for posting back. Looks like you repaired it. Good job.

Regards.

 

[pm-r]

I’ve sorted both sides out to be sure and pieces it back together. So far it’s been running around an hour and hasn’t gone off. So fingers crossed you were correct with the screen diagnosis.

Yes, thanks for the feedback and congratulations on your fixing capabilities.

I get concerned when I read about any problems with any 2011 iMac, that I and now my wife also has as uses.

Except for the fact that ours are mid-2011 and the 27" models.




- Patrick
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