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Trying to install (from usb) Ubuntu-12.04-desktop-amd64, but monitor turns off after select Install Ubuntu on Hard Drive. PC keeps working. Video is AMD Radeon HD 6790 and CPU - AMD Phenom II x6 1075T Sorry for my English.

PS. With ubuntu-12.04-desktop-i386 i've the same problem.

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up vote 2 down vote accepted

I had this issue as well. The way that I got around it for the install was to press f6 at the boot prompt and choose nomodeset. then press esc and type xforcevesa on the command line in the boot prompt and then press enter.

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In case with USB I couldn't find the way to set "nomodeset" option, but while installing from CD this option is available. Thank you for help. – Madmax Apr 27 '12 at 5:31

does it finish the install or you cant tell ??? its the graphics drivers find out how to install the drivers from command prompt if install finshes you should be able to get to boot menu and repair and a prompt then you just need to install the raedon drivers i dont have rae i have nvidia so im not sure but it might be as simple as sudo apt-get install radeon and update update get all updates and upgrades u can

sudo apt-get update && sudo apt-get upgrade

even if you need to run these from the thumbdrive prompt it could still fix the install

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I had exactly the same problem but left the computer to finish the instal and just switched off. On reboot it worked fine but now if I leave the computer for a time the screen turn off and won't turn back on. I can log in via ssh but I cannot get the diplay back without a reboot. – Frank May 19 '12 at 16:50

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