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Author Topic: iMac 27" Vid Problems  (Read 169 times)

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Offline Slappy

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iMac 27" Vid Problems
« on: September 10, 2019, 09:27:45 PM »
Pretty sure I know the solution (haul it to a Mac shop) but, has anybody seen anything like this with a late 2016 iMac? It's the base model, i5 3.2GHz, Radeon R9 M380 2GB, blah blah blah. In the first few months I had it, there were LOTS of weird graphic glitches, then it calmed down.

After updating to Mojave last week (may be a coincidence) twice now I've gotten this half-screen, and it also flickers so I can barely quit all the apps before I Restart. Once I just had to power-button it since I couldn't even see the menus.

I don't have any temp monitoring software and I'm not even sure if I did I could see it once the glitch takes over, but what's good, free & maybe captures a log file I can look at after I restart?
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Offline Joe

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Re: iMac 27" Vid Problems
« Reply #1 on: September 10, 2019, 10:36:53 PM »
Since you recently updated to Mojave I would reset the PRAM.

  • Shut down your machine. Yes, all the way down, not sleep or logging out.
  • Press the power button and then press command-option-p-r. You have to make sure you get those keys pressed before the gray screen comes up or it won’t work.
  • Hold those keys down until your Mac reboots again and you here the startup chime.
  • Let go of the keys and let your Mac reboot normally.

And then I would reset the SMC.

For Mac Minis, Mac Pros, iMacs, and Xserves (really on a server?):

  • Shut the machine down
  • Unplug it from the power
  • Press and hold the power button for 5 seconds
  • Plug it back in and turn it on.

And then see if it still does it after that. If it does I'd say the video on the logic board is going out. Used to be you could replace the video card on the logic board on iMacs. I doubt if that is still possible the way Apple has tried to lock everything down the last few years to keep people from upgrading/repairing their own machines.
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Offline scottrsimons

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Re: iMac 27" Vid Problems
« Reply #2 on: September 11, 2019, 09:29:14 AM »
How hot does your iMac feel at that point? Be a bit touchy feely with it, around it's back side. Does it feel quite warm, or even hot? If so, unplug it and try to blow it out. One vent in the back above the power plug, and then all along the bottom of the iMac is a vent. Make sure all are clear of debris and nothing is blocking them. You might not be getting good air flow, and thus your iMac is over heating.

Could also get a small desktop fan and keep it running on the iMac. I have on that is powered by USB. Which I like to have there for heat, but also to let me know if my Mac is powered up or not. Very easy tell.
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Offline Slappy

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Re: iMac 27" Vid Problems
« Reply #3 on: September 13, 2019, 12:20:11 PM »
Thanks guys! I did both, man there was a fair amount of crap in those vents, esp the top ones.

I need to buy a little comp vac - probably better to suck out than blow in.
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Offline pspdfppdfxhd

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Re: iMac 27" Vid Problems
« Reply #4 on: September 13, 2019, 12:21:13 PM »
Ah yes, the age old question: "Suck or Blow".

 :drunk3:

Offline Joe

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Re: iMac 27" Vid Problems
« Reply #5 on: September 13, 2019, 12:22:43 PM »
Thanks guys! I did both, man there was a fair amount of crap in those vents, esp the top ones.

I need to buy a little comp vac - probably better to suck out than blow in.

The vacuum can cause static so beware of that.
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