MacBookPro4,1 - irregular crashes, usually when power connects

Discussion in 'MacBook Pro' started by x30n, Dec 31, 2011.

  1. x30n macrumors newbie

    Apr 17, 2007
    Hi all,

    I have a MacBookPro4,1 (non unibody) which gives me a hard time during mobile usage.

    While using it connected to the power, not moving it, the Book works fine for weeks. During mobile usage however there is a potential risk of a system crash. It does usually manifest in a flickering screen, sometimes total image distortion. The highest chance to see this behavior exists when I plug the power back in. Usually the image flickers and the machine is dead.

    Here is what I did to figure out the source of the problem so far:

    • I had the nvidia chip tested at the local Apple Store. Since the board has been changed because of that I didn't really suspect it to be the problem any longer.
    • They also ran a basic check of all components. None of them seem to be trouble makers.
    • I checked the Memory using memtest and TechTool Pro. Seems OK.
    • The HDD is relatively new. Tests conducted by TechTool Pro could not detect any problems.
    • I've reinstalled the OS, avoided usage of any programs not coming from apple.
    • I've noticed that the book is at high risk to crash when using ScreenFlow or Skype (which I'll never use again anyway, but still)
    • The battery check is OK. Should have around 200 cycles left before being useless. The battery itselt is new, an original spare part from Apple.
    • The crashes are not gray screen of death.
    • Quite often, when booting on battery, thescreen backlight goes crazy. It looks like spotlights coming from the bottom. I think this is because only half of the lamps turn on. I don't know if this is related to the crashes, yet I consider it worth mentioning. Sending the book to sleep and waking it up again usually fixes the problem. Again, the problem does not seem to appear when connected to the power supply.

    So far I rule out RAM and HDD. I do however suspect a magnetic spike or something when connecting the power supply causing a some data connection to go crazy. Is this possible? After all I did place the new HDD in the book myself. Could I have removed some magnetic shielding without noticing?

    Does anybody else observe this problem? Any solutions?

    Any ideas on how to find the cause of the problem?

    Thanks a lot!



    Just did one more test. While techtool pro performed graphic RAM checks (I ran 10 in a row) I've unplugged the book just to plug it in again. The moment I plug in the book a distotion is visible. Its one pixel high and spans from one end of the screen to the other. Since the "clean" test shows only white, shades of gray and black, its strange to see a line of different colored pixels. It almost looks as if the values stored in the GPU Memory are no longer right.

    Maybe a clue.

  2. m85476585 macrumors 65816

    Feb 26, 2008
    It sounds like a bad GPU. Software tests can't always find a hardware problem. I wouldn't give much weight to Techtool Pro tests. And I've had bad RAM that Memtest never found.

    A bad hard drive wouldn't cause the problems you are having. It would have to be something on the logic board or part of the power system. There aren't really any user serviceable parts there, so you probably need to have a new logic board put in, or convince Apple to do it for free since it's a GPU problem and should be covered by an extended warranty.

    I've had the spotlights from the bottom problem two or three times with mine, but every time I just reboot again and it's fine.

    A few things to try:
    -Try stressing the GPU to see if the problem happens. Maybe try playing a video game with 3D graphics. I know Skype uses the GPU for some reason, and Screenflow probably asks it to do more work than normal as well. A video game should really stress it.
    -You could try a different Magsafe, but it sounds like the problem is mostly caused by battery power, so I doubt that would help.
    -If you have any other compatible RAM around the house you could try that, but I don't think it's a RAM problem. Bad RAM would not really cause artifacts on the screen (you don't have integrated graphics that shares system RAM). Bad RAM typically causes kernel panics, data corruption, and general instability.
    -Could be a loose or broken ribbon cable internally, but it doesn't sound like it.
    -You could try to replace the thermal paste for the GPU and CPU, but it's an involved process and you are likely to make things worse if you don't know what you are doing. Also, that will probably just make the problem harder to spot without fixing the root cause.
  3. x30n thread starter macrumors newbie

    Apr 17, 2007

    thanks for your suggestions. When I had my initial problems with the nvidia chip I did replace the thermal paste. I think I did a much better job than apple. The original paste was really messy. It may be a good idea trying that. Too bad its such a lot of effort.

    I did clean the dust of the board some days ago, just to rule out some unwanted short circuit. Didn't do any good.

    What did good however was my decission to give Lion a try. So I went to the Apple Store again getting one of these USB Sticks which seemed like a really big deal to them. Guess nobody is ever asking them for it :D

    Bottom Line is that since I'm running Lion it never crashed so far. I did use it for three days streigt. At work and at home. Does a fine job. Maybe the ne GPU drivers fixed something. No idea.

    I'll give the GPU something to sweat. Should have a few Steam Games running on the Mac.

    Thanks for your help!

  4. x30n thread starter macrumors newbie

    Apr 17, 2007
    Looks as if I've celebrated too soon. I managed to crash the book repeatedly through an attempt to watch a video using flash. Now flash is a bag of pain anyway, so I consider getting rid of it.

    I've also found the 2GB of original RAM that came with the book. Even so the crash could not be reproduced the video did still cause a disturbance. I don't think the RAM causes the trouble. I'll keep it for now anyway.

    Nevertheless I think I've got to get a new mac. For now I bought a 2006 MBP which came cheap. It should help me bridge the waiting time until new MacBook Airs appear in the stores. Selling my current book as defective will decrease its value, yet even defective books are usually sold quite well these days :|


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