2015 iMac 5K 27" random flickering screen - does seem to 'fix' on reboot

caincha

macrumors member
Original poster
Jul 15, 2012
61
7
I've done some research and it seems more people have the same issue.

This video ain't mine (so far my issue ain't that bad only similar):




It can go days with no issues and then it happens usually starts when I'm scrolling through my mails on Outlook and when it does start even checking my apps on the dock (Dock's amplifier effect) triggers it as well.

Then I reboot and all is well for days…

What is that? Could it be faulty cable or a software issue maybe a firmware thing or even something with Mojave's Metal…?



Oh and I've seen the copy/paste reply sent to others online saying ‘replace display here's the guide’. That's not what I'm after.

First those displays are almost as expensive as the iMac itself but also other than this random flickering it works fine there has to be an answer other than the usual Apple motto ‘pay heaps of cash to replace or a truckload of money to buy brand new’.

Doesn't anyone knows how to actually fix this…?
 

RyanXM

macrumors 6502
Jul 7, 2012
332
352
DFW, TX
This seems like a power supply related issue. Does it change with brightness level? Stress level?
 

goslowjoe

Suspended
Dec 22, 2017
125
88
I had the same problem. It turned out to be a failing logic board. It was replaced even after my AppleCare warranty had run out (the story is in another thread on this forum).
 
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goslowjoe

Suspended
Dec 22, 2017
125
88
Can you elaborate on that as in what sort of failure it had…?
The screen was replaced in January to solve a problem with dust in the corners and point tinting all round the edges. Within a month the screen started flickering. I reported this and the Apple Service Centre tested it. They said there was an imminent failure of the logic board on the horizon. I thought it was strange as I had no other problems.

The result was that they replaced the screen again, and replaced the logic board. I asked what had happened but they merely said that their diagnostic tests showed it was going to fail.
 

caincha

macrumors member
Original poster
Jul 15, 2012
61
7
The result was that they replaced the screen again, and replaced the logic board. I asked what had happened but they merely said that their diagnostic tests showed it was going to fail.
Thanks for sharing :)

Sounds like they botched the first time they replaced the display and came up with an excuse to replace it again…
The information I have so far is that the T-Con board can be easily damaged and the issue would be one of those chips on that board - but which chip and why that happens is still a mystery to me:






 

goslowjoe

Suspended
Dec 22, 2017
125
88
Caincha, they screwed up even more, and I was furious!

My closest Apple Service Centre is some 280km from my home, and so the round trip to collect the unit was an eight-hour outing. Got the iMac and drove home. On my return I found that they never ran the blank board serialiser, and so my iMac showed up simply as "iMac" with no further details or serial number. I had never had something like this happen and the results were (un)expected - few things worked and technically I had a perfectly illegal iMac. After some frustrating comms by telephone and email, I had to do the journey again the next day. Running the BBS procedure took only a few minutes. Obviously there was no proper worksheet indicating what was supposed to be done to complete the process.

The hard lesson I learnt here: NEVER, EVER, accept anything that was supposedly fixed or replaced by Apple (or any other supplier of whatever service was rendered) without checking the work done BEFORE you leave the store!
 
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