Imac screen black after SMC reset???

Hi. I have problems - big problems with my Imac 27 inch mid 2011 (bought it used - not functioning). Firstly - when i started the mac there was a box in the middle of the screen with a question mark. Then i tried to make a pram and smc reset, and now the screen is completely blackSad. I then found a thunderbolt cable. Attached the bad Imac to another functioning Imac i have (27 inch mid 2013 model). The I started up the bad Imac in target disk mode. To my surprise there came a mounted disk on my functioning mac. The problem here was, that there were no files on the harddrive - at all! I then installed El Capitan on it. Started the bad Imac again - still black screen. I have then tried to make target display mode to my functioning Imac. It works, and i get picture from my "bad" Imac. What is wrong with it? Is it the display (or how can i find this out?) or is it the graphics card? Why did it go black after SMC reset ?? Someone told me, that isolated it should be the LCD that is failing or the connection to it. ? Please help meHappy

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Basically you've found it needs repair.

I can't guess what spares you have but did you take a voltage reading on the battery inside?

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What kind of battery? Pram battery?

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Varies with model.

I find a visual, some google work to help a lot plus a DVM to see if it's dead.

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Could this have something to do with the black screen?

Do the PRAM battery not only store date and time and so? How could this affect a black screen?

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Now that would take a lot more inside knowledge.

As Apple didn't open source the code in there product no one can really drill down into why I've seen that happen. I hope you can accept that it's one of my checks that takes about 20 seconds once the machine is open. If the battery is gone, odd things can happen, and not all models have them.

I'm encountering techs and some self repair folk that want an absolute, it's going to roll double answers. For that you may upset them to tell them that's what happens at service counters. The shop techs have a routine or list of things they do and I'll share something I'll do that I don't think too deeply about. I have dozens of machines to fix so I have a list of things I check. Your machine is old so let's check that.

If you want to know why it may affect screens and more, well, Apple would have to publish the design, code for us to pull out and walk through how this could happen. That is unlikely.

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The box with the question mark inside it was your first clue

This means that there is either;
1. No hard drive installed
2. A hard drive with no working System Folder
3. A hard drive that is defective.

Not sure why you were surprised about the "bad" disk appearing on the good iMac when the bad iMac was in Target Mode. That's what it does.

Do the SMC /PRAM again and reboot holding down the "R" key.
This is Recovery mode and will allow you to install El Capitan again, should you wish to.

Bought used, not functioning. Could have multiple things wrong with it.


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Disk question mark

Yes - firstly the question box appeared. Afterwards I did the PRAM / SMC reset. The result of that were a total black screen. I can't see the screen anymore - only during target display mode to my other mac.

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Machine is running

The machine is actually running fine, but only through my second display. Would this mean that the GPU is okay, and the fault lies in the LCD or some cables? I have tried the PRAM and SMC many times. Wont work. The PRAM reset works fine, and the computer reacts on it that it should do, but when i do SMC, I can't see what happens. Reading on the internet, there is in many "types" of doing SMC reset. Apple says that you should unplug power cable - then wait 15 seconds. Plug it back in wait 5 seconds, and then turn on. Some other lige "We are JIGsaw 24" on youtube says that you should hold down CMD SHIFT ALT option key during press on the power button? I have basically tried all, none of them worksSad

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Did I miss the part about the "second monitor"?

How is this second monitor connected to the non-functioning iMac?

If it is via the Thunderbolt connection, then that would indicate that the GPU is working as designed and that the problem lies elsewhere.

With the iMac running, shine a bright light onto the screen. You may have to get real close, and see if you can see any of the regular screen icons there. They will be really dim, but should be visible.
If there are any visible, then the LCD is OK but the backlight LED's are not functioning.

Time to pop the screen out and check ALL the wiring on the back of the LCD and their associated connections in the body of the iMac.


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Hi again

Yes i have user a thunderbolt cable. The screen is displayed fine on the other iMac. But the one I have problems with still has a black screen. It is very annoyingSad I have tried to shine a bright white light upon the display - nothing to see. I also think it's time to pop of the lad and check up on the connections. But I still think it is very odd, that the black screen came after pram And smc reset - how can this be?

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Still concerned about the "Second Monitor"

This would NOT be the other iMac as there is no way to get the video from the broken one into the good one.

So, have you tried another, NOT an iMac, monitor on the broken one?

Good idea to open it up and check the connections but I would not obsess on the PRAM and SMC reset too much.
Granted it "may" be connected but there is nothing you can do at this time.


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