Model A1297 Unibody: Early 2009, Mid 2009, Mid 2010 & Late 2011

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Scrambled graphics at login screen and blue screen after login.

My MacBook Pro has recently be running a bit slower than usual, nothing too drastic, however just before the login screen appears it shows as scrambled/pixelated blocks of colours. It lasts a few seconds and then I can login as normal. After I login I see my desktop but shortly after it goes blue for a few seconds and then back to normal. Can anyone help with what this could be? I have tried the following to resolve the issues but they still remain.

- Clean install of Mountain Lion from backup and setup as new (after non fixable disk errors. There are now no errors)

- Reset PRAM

- Reset SMC

- Boot and restart in safe mode

- Create new user account

- Running quick and full Apple Hardware test which found nothing wrong.

I will try and get photos/videos up as soon as I can.

Thanks!

Update

Included are the images. The first is the blue screen after login. The second is seen prior to login and the third is also seen prior to login but after restarting rather than shutting down and turning the mac back on.

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Chosen Solution

Hook it up to an external monitor to see if it's a GPU issue.

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Comments:

Thanks! Will try that! Does it need to be so its just visible on my external monitor?

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This will help determine if you have a processor issue or the problem is with the cabling or screen.

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I have my monitor connected via HDMI. The blue screen still appears after I login on both the mac and monitor

With the monitor connected I'm not seeing the distortion at all on either before the login screen appears. I've done around 8 reboots. I've also toggled the graphics options in energy saver and again Im not getting distortion on either screen.

Whenever I unplug the monitor I see slight distortion which disappears with a second or two.

With no monitor connected I do almost every time get distortion. It seems to come in 2 types. Pixelation or just blocks of yellow and black.

by

I see the yellow blocks when I choose shutdown and power on but with restart I see the pixelation type distortion. Trying to capture video now.

Interestingly logging off and logging rather than restarting results in no blue screen.

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What operating system are you running?

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