My iMac screen goes all psychedelic rainbow after wakeup. The rainbow screen only lasts a few seconds then goes back to normal screen. I'm curious if this is a software update issue or a graphics card going bad issue? Everything was perfect before the last update. Any suggestions are welcome. Thanks.
Mac specs: Retina 5K, 27-inch, late 2015
Processor 4GHz Intel Core i7
Graphics: AMD Radeon R9 M390
iMac 27", macOS 10.14
Wow! It certainly looks like a GPU going bad to me. Have you by an chance tried to reset the PRAM?:
1. Press and simultaneously hold down the following four keys during the startup process. You should do this from a cold boot. That is, after you have completely shut down your Mac:
COMMAND + OPTION + P + R
2. Continue holding down all four keys until one of the following conditions occurs:
a. About 20 seconds passes, during which time your Mac may appear to restart.
b. You hear the startup sound a second time.
c. The Apple logo appears and disappears for the second time.
3. Release the COMMAND + OPTION + P + R keys after one of the above three things occurs.
Maintenance Tip: It is highly advisable to zap the PRAM about every six months or so, in order to keep your Macintosh running smoothly and efficiently.
Resetting the SMC may possibly also help:
1. Shut down your machine.
2. Hold down the power button for about 10 seconds.
3. Release the power button and wait a few seconds.
4. Restart your computer.
5. If the problem still persists, shut down your machine again.
6. Unplug the power cord.
7. Wait about 15 seconds.
8. Reconnect the power cord.
9. Wait another five seconds.
10. Restart your machine.
I hope you find the above info useful. :)
Wow! It certainly looks like a GPU going bad to me. Have you by an chance tried to reset the PRAM?:
1. Press and simultaneously hold down the following four keys during the startup process. You should do this from a cold boot. That is, after you have completely shut down your Mac:
COMMAND + OPTION + P + R
2. Continue holding down all four keys until one of the following conditions occurs:
a. About 20 seconds passes, during which time your Mac may appear to restart.
b. You hear the startup sound a second time.
c. The Apple logo appears and disappears for the second time.
3. Release the COMMAND + OPTION + P + R keys after one of the above three things occurs.
Maintenance Tip: It is highly advisable to zap the PRAM about every six months or so, in order to keep your Macintosh running smoothly and efficiently.
Resetting the SMC may possibly also help:
1. Shut down your machine.
2. Hold down the power button for about 10 seconds.
3. Release the power button and wait a few seconds.
4. Restart your computer.
5. If the problem still persists, shut down your machine again.
6. Unplug the power cord.
7. Wait about 15 seconds.
8. Reconnect the power cord.
9. Wait another five seconds.
10. Restart your machine.
I hope you find the above info useful. :)
Please let us know how it goes. GPU issues -- if that is indeed what it is -- are no fun, and usually mean the death of a machine. Particularly if it is an old laptop, because it means having to replace the entire motherboard, since the GPU is soldered to it. It is very hard to come by a motherboard for an old MBP. Plus they are majorly expensive. I speak from experience. At least you've got an iMac, so maybe it is recoverable.
Sadly my *fingers crossed didn't work. I am in the middle of a huge project so this is horrible timing. My computer still seems to work ok... its just when the screensaver and energy saver kick in the screen goes funky. I have been shutting down every night and turning on only to use and not letting the screensaver start and everything seems to work ok for now. It's probably only a matter of time before it decides to kick the bucket. I have done what I can to back up everything I have. Sadly I've only had my computer for 2 years.... I was so hopeful it would last 10+ yrs like my Mac before.
Thanks for your help. :) I am all ears if you have any other ideas to try.
Yeah, sadly, I didn't really think that it was going to work, but I didn't want to say anything, because I didn't want to dampen your spirit. I am very surprised though, because that definitely should not be happening if your machine is only two years old. If there is an Apple Store in your area, I would definitely take it in. If you have a three-year Apple Care package -- very wise to get -- it will STILL be under warranty, and shouldn't cost you anything to get it repaired, even if they have to replace the expensive GPU. I don't know if it is soldered to the motherboard in an iMac or not. Anyway, given the age of your iMac, personally, I would not accept it or live with it. I would take it in. After all, for many of us, these are major investments, and we expect to get a good return on our money, right?
Thank you! I will give this a try and hope for the best. *fingers crossed
10.14.3 update - rainbow screen after wakeup
