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Question

MBP Video Tearing

Oct 26, 2011 11:01AM PDT

Not expecting much out of this one, but on the outside chance someone may have a thought, why not.

Unit is a Mid-2010 15" MBP, in for video tearing, and has been in twice before.

First time it comes in, I diagnose a bad MLB (Main Logic Board) because the video tearing only happens on the internal display, not external. So I replace the MLB.

Second time the unit comes in, ASD reports that the GPU is running under voltage. Verified this by looping the test 10 times, and each time a failure. Replace the MLB again.

Back again for the same issue. This time I've noticed that it will happen with ASD OS, but not ASD EFI. It doesn't happen with AST, or just letting the unit sit at the EFI boot selection screen. I safe boot a known good OS, problem doesn't happen. If I boot normally, I can trigger the problem reliably by putting the mouse cursor at the top of the display or along the left edge. Right and bottom edges do not trigger this, and there are a few isolated areas on the rest of the display that seem to trigger it. So I figure maybe the unit has bad RAM, and I run ASD EFI which has more detailed RAM checks, which all pass. ASD OS also passes which does video controller tests. I also run the new AST VST which checks for issues similar to this, and it comes up clean.

I also notice that the instant I plug in the MDP connector for an external display, the issue goes away. So when the unit switches from internal graphics to discreet, the problem vanishes. Curiously, if I disconnect the external display, I am left unable to trigger the issue until I reboot the unit.

So everything seems to be pointing to there being an issue with complex drawing operations with the integrated graphics, but the odd part is that I have had three MLBs now, IN A ROW, which exhibit the same problem. While not out of the question, the odds are pretty far out there. Apple's DOA rate is pretty low, and to get three boards in a row which have the same problem.

At this point, unless I come up with some brilliant insight before I get into work tomorrow, I'll be ordering another MLB. The three boards in a row with the same issue is what keeps sticking out at me. I just can't find any symptoms that don't point to a bad GPU that I haven't already ruled out. So, on the outside chance someone here might have said brilliant insight, posting this. Otherwise, you can think of it as a slightly out of the ordinary day in the life of an Apple tech. Something to keep in mind the next time you have to take a computer in. This is a sample of what goes on.

Discussion is locked

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Answer
No answer, but an observation
Oct 26, 2011 9:42PM PDT

At this point, Apple starts to frown on the AASP as they now tend to believe that the Tech doesn't know what he is doing and who keeps ordering the same part, for the same repair, more than once.

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That may be
Oct 27, 2011 10:23AM PDT

That may be, but I stumped their TSPS people as well, who came to the same conclusion. It's highly odd that I'd have this problem on three separate boards, but everything points to a bad IG chip.

Only other possibility I can come up with is a short in the case, which should be impossible since there's an EMI gasket covering the entire area by the MLB. And it wouldn't explain why the problems go away when the external video is connected, and doesn't come back when it's removed.