Some random screen flickering on MBP (A1211)

[vorob]

It's a C2d machine with ATI X1600, 15 inch. Everything is fine but sometimes screen blinks without a reason. Take a look:

Video is in slo-mo, in real it's much faster.

What can it be? Just happens randomly. Not sure what causes it, but I think maybe it happens when I work in custom browsers (firefox legacy or chromium), but maybe no...

I also thought about CCFL, but it's not light off, it's more like fast color change...

 

[theMarble]

Which OS are you running? Mavericks on the X1600 has some GPU problems.

 

[vorob]

OSX Lion

 

[rampancy]

Very odd. I don't think it's your GPU; brightness changes like that make me think that there is indeed a problem with your LCD's CCFL.

 

[vorob]

I did this thing https://support.apple.com/en-us/HT201295 and looks like issue is not happening anymore. Will look further...

Any chance this reset could really help, or it is self complacency?

 

[vorob]

Nope, no luck. Still happens sometime.

 

[vorob]

My biggest problem here is that it happens randomly. It can be several hours without it or it can be several blinks within 10 minutes. And I also don’t know how to provoke the issue so I can’t even think about any fixes here.

 

[Amethyst1]

Does it also happen in the boot menu (hold [Alt]/[Option] after powering on), i.e. before an OS has booted?

Can you trigger the issue by quickly moving the lid (as if to open/close the laptop)?

 

[vorob]

No issue with the lid no matter what i do with it

I have a guess it has smth to do with power. Like cpu start eating more voltage and it blinks, or gpu switches from power-saving clock to performance (no sure is x1600 do this at all, just a guess).

As for boot menu... See, to catch this issue i have to sit and do smth with computer. Otherwise it's impossible to catch it.

I hate floating issues!

 

[Amethyst1]

If you think it's related to power, try using the machine without the battery, which downclocks the CPU to 1 GHz.

You can also try booting in Safe Mode by holding [Shift] immediately after powering on. This skips loading GPU drivers and disables graphics acceleration, among other things.

 

[vorob]

Ye, that's an idea, thanks. The problem is that blinks happen randomly. Like i said it could happen right away, or after 3 hours. So you have to use use and use the machine...

 

[rampancy]

Amethyst1's tips will likely help isolate the cause of the issue, which may help you figure out a fix. Booting in Safe Mode will help rule out a software-related cause (short of you doing a clean reinstall of OS X, which I doubt you want to do). Booting without a battery will also help you figure out if it's indeed a power issue -- if the issue happens with the system downclocked (due to the battery being removed), then it's likely not a power issue and more likely an issue with the display.

Another suggestion is to run your machine on an external monitor. If the issue happens while using an external display, then it's likely a GPU issue.

 

[Amethyst1]

Booting in Safe Mode will help rule out a software-related cause […]

If the issue doesn’t arise without graphics acceleration, this may also point to the GPU.

 

[vorob]

I decided to switch from OSX Lion to OSX Snow Leopard, plus i've installed Windows 7. I've been testing computer for some time and so far i didn't see any flickering. Maybe it was software issue on Lion.