Hello, my name is***** and I will try to assist you today. Please tell me if you know the update that was applied? If you do not know that is fine, just checking to see if you recall which update was applied.
And to be clear so that I understand, your iMac applied the update and then attempted to reboot? Meaning after it installed the update, it turned itself off and then back on, and now it only gets about half way through the boot up procedure and stops? What does it show on the screen? Also do you have a hard drive light showing any activity?
Thanks for getting back to me. Did you ask this question 2 times on here? I see another question that basically has the same question?
Alright, let me first close that other question out so that you will not be charged for both questions. Please give me a minute to do that okay?
Alright, I submitted the other one for closure and if it gets charged you will get a refund for that question.
So back to your issue...
Please tell me what is the latest version of OS your using. Is it Yosemite?
Also is this a MacBook Pro or MacBook Air?
Ok, thanks for the replies. I would like you to follow the instructions below on how to reset the SMC as a first step to fix the black screen locking issue.
On any modern Mac with a built-in battery, which is just about all of them nowadays, this is how you do that:
Then reply and let me know if it booted normally, if it did the same thing, or did something different happen?
Okay, it is suggested to do this a few times before moving to the next step. Please try it a few more times ensuring your holding all the keys at the same time. Then let em know if it is the same.
Okay, thanks for doing that. Lets move to the next step...
Oddly enough, this seems to work to resolve some of the mystery Mac booting into black screen issues. Here’s the precise sequence to follow:
Okay, there is one other step I can think of...
If the above two tricks failed, a PRAM reset can often do the trick. As a potential solution to the black screen on boot, this is done upon restarting the Mac similar to an SMC reset:
Try those steps above and let me know. Thanks
So do you ever get the Apple logo?
The Apple logo comes up right after the sound should be heard. Try the steps again from my last instructions, and make sure you hold all the keys listed prior to the logo appearing.
Alright, this is a strange one. Let me do some digging and get back to you shortly. Should only be a few to 10 minutes.
Glad to hear, I thought I typed in the suggestion to try an external monitor here previously, but do not see it. I must have sent it to another customer.
Yep, I found it... So sorry. You must have thought I forgot about you, when truly I had not. Here is what I sent to another customer by accident instead of to you.
One thing you can also try is to hook up an external monitor. I found a few people have had this happen only to find that they somehow changed the display to an external monitor. Once they hooked up an external monitor they were able to make the settings to return it to the screen they wanted.