MacPro 2013 Yosemite -- won't start up, monitor never turns on, repeatedly reboots itself

I have been having the same problem and stupidly tried a reinstall and recovery from Time Machine (docs only no apps) which has caused me to persist with this white screen problem for 4 days now. I eventiually reached point where I needed to reinstall from the Internet and it reinstalled Lion and u upgraded directly to Yosemite (MISTAKE!!!), this cause the white screen to return.

After a multitudes of restarts and forced power offs I held down the shift key as described in Charlie's post and this eventually got me up, but only barely running. I have noticed that screen refreshes are VERY slow and you can count the screen refresh increments as it is very visible.

I only have one display (iMac 27" Mid 2011, 3.4GHz i7, 32MB RAM, 2TB HDD, AMD Radeon HD 6970M 1024MB) this white screen crap all started a day or so after installing Yosemite, but I was spending some time installing Android Studio and it did require for me to install Java SDK from the Apple download site Rel 6 I think???)

Anyway, holding the shift key managed to get me up, thanks; but I am still broken - Apple, you need to pick up your game!

Rick

I have exactly the same problem as you, on a macbook pro mid 2010 model. I can't see any slots for a genius bar appointment on Regent Street. I installed Yosemite and it was running just fine for a few days then suddenly I was hit with this. Suffice to say I'm not best pleased.

Things have taken a bad turn, my iMac is now useless. I have to reinstall yet again, but before I do I will give apple a call to try and get a hint of what I can do to recover the situation. My 27" imac is too big to carry into the shop as I am not able to carry it.

very upset with the whole situation

Out of interest, what was the hardware in this case? Mine is a MBP mid 2010 and I can't get it to boot from an external USB stick using the option-boot trick.

This worked for me, too! Couldn't believe it when I hit the screen with my flashlight and actually saw everything. Thanks for posting.

Hey if anyone is still having issues then check this out:

I had the same problem with the black screen startup and reset password loop- but no startup chime so I couldn't seem to boot to safe mode or anything. Finally I realised you can just hold down Command+Option+P+R from right after you turn on the Macbook and keep holding it down until the computer actually restarts, it then simply asked for my password (the screen was black, I used a torch as some of you suggested here) and did it's thing.

I have the same problem, but as much as the replies have helped other people, all the terms used are quite foreign to me so otherwise unhelpful. Can someone please explain in layman's terms what i need to do to stop my macbook from randomly shutting down. Thank you

My issues are on an iMac 27" 3.4 Quad Core 17 Mid 2011 and I am having an engineer pop over this afternoon to replace the video card under the iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program. Hopefully that will get my machine up and reliable once again.

My Macbook Pro is suffering from different issues post-yosimite, and we are woking through those one by one.

Thank you! I did the flashlight trick and my computer is back to normal. Anyone who hasn't tried this should try it now.

This worked for me as well. Thanks! The 10.10.1 System update fixed this problem for good. My MacBook Pro Mid-2010 works fine now.

I had exact same problem. Thank you for sharing your solution. I will try it tonight.

It sounded like I need to have external drive with Mac OS 10.x

I can't remember when I put my Mac OS .

Grant Bennet-Alder wrote:

Don't neglect Safe Mode -- it was intended to be available for rescuing you after bad Settings or Bad Additions to Mac OS X.

Hold down the Shift key at Startup. It also does one pass of Disk Utility ( Repair Disk) as it starts up.

This solved my problem, first I disconected my second monitor, then i boot up the machine while holding shift (safe mode) white screen with apple icon and loading bar appears and takes a longg time, once its done loading it will open in Safe mode, you will be able to log in, monitor might be glitchy as in white lineas appear or starts flickering, a message appears that some installs need to be done, click ok computer sytarts installing the software update, it gets donde and gets you back to your desktop after that restar computer with only one monitor and everything will work fine, after that you can turn it off connect your second monitor and get back to work

If I was having any more kids, I'd name the next one after you! Thanks for the fix - works now!

I have the same problem with Mac Pro: Monitor did not turnOn! I must hold power button, turn Mac off and turn once more On. After that appear screen for solve a problem.... What happened with Apple?????? Its really bad... i can't choose best for my monitor resolution, can't without a problem turn it On... ****!!!!! 😟 Apple, i am WERY ANGRI!!! its cost a lot of money!!!! Do something !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

TThanks for that, the torch trick was great clue, all sorted now! Awesome help!,