2014 iMac screen goes black but not in safe mode.

[BritishB0xer]

Model: Apple iMac 27" i7 5k 4GHz 3TB ƒ 2014
Issue: Screen goes black after 4 mins of playing videos, then continues in shorter intervals.
Graphics Card: AMD Radeon R9 M295X 4 GO
Tests: Both Etrecheck and Apple diagnostics (reboot) show no signs of conflicts by software or hardware.
Functional: YES-The Screen functions as normal in safe mode., never black again., But no audio works in safe mode.
It also works fine with out safemode if rebooter with the power button down before plugging in the power cord resulting in a very loud fan.

I erased the fusion drive, rebooted in recovery to install a fresh system this computer came with, no iCloud user, yet same problem continued, I then erased again and installed Catalina, after 1 hour the problem continued, then i did the same with BigSur.

I think my imac has some sort of issue with firmware cause the screen started going black after i upgraded to Catalina, i then went to BigSur and the issue came back.

I Called an non authorised Apple repair person who suggested that my imac needs a new video card and i should buy it at the Apple store, but when i told him the screen works fine in safeboot he stated that its using the computer graphic card not the (graphic card) and none of this makes sense to me, is it using the one and only graphic card it came with to work with the 5k screen or are there two?

Some more details
Model Name: iMac
Model Identifier: Mac15,1
Processor Name: Quad-Core Intel Core i7
Processor Speed: 4GHz
Number Of Processors: 1
Total Number Of Cores: 4
L2 Cache (per core): 256 KB
L3 Cache: 8 MB
Memory: 32 GB
Boot ROM Version: 431.140.6.0.0
SMC Version (system): 2.23f11
Graphics Card: AMD Radeon R9 M295X 4 GO

 

[BritishB0xer]

Btw i just found out some people changed the graphics cards yet the problem of over heating continued on their machines, thought i mention that i dont see and indication of over heating on my imac

 

[BritishB0xer]

bump

 

[Willo34]

Graphics card seems unlikely to me. Not a known issue with those machines. Could still be a problem with the Fusion Drive, they break all the time, not uncommon that you can start-up in safe mode....more likely FD problem or even RAM then the graphics card I would suggest.

 

[BritishB0xer]

Graphics card seems unlikely to me. Not a known issue with those machines. Could still be a problem with the Fusion Drive, they break all the time, not uncommon that you can start-up in safe mode....more likely FD problem or even RAM then the graphics card I would suggest.

should i try booting off a ext ssd with the fusion drive un mounted to see if it happens?

 

[Fishrrman]

It's probably a graphics card failure.

When you boot into safe mode, you are BYPASSING the graphics card, using only the CPU's "integrated" graphics.

That's why safe mode works, but "normal" booting (which always tries to use the graphics card) may not.

Solution:
Replace the graphics card.
At going on 8 years old, it would probably be wiser to look for a replacement iMac...

 

[BritishB0xer]

It's probably a graphics card failure.

When you boot into safe mode, you are BYPASSING the graphics card, using only the CPU's "integrated" graphics.

That's why safe mode works, but "normal" booting (which always tries to use the graphics card) may not.

Solution:
Replace the graphics card.
At going on 8 years old, it would probably be wiser to look for a replacement iMac...

This is exactly what i was asking about, is there some other integrated graphics route or not.,
cant i by pass the graphics card in normal mode? And whats the actual differences between them, memory??

 

[Fishrrman]

"This is exactly what i was asking about, is there some other integrated graphics route or not.,
cant i by pass the graphics card in normal mode?"

You can do it by always booting into safe mode, but that won't let you load extensions, etc.
This might or might not work for you in day-to-day usage.

There's a long thread in the MacBook Pro forum describing how to disable the discrete graphics on MacBook Pro's that have the "RadeonGate" problem.

I don't know if this could be applied to iMacs (I'm guessing, not). I just don't know.

"And whats the actual differences between them, memory??"

Performance, mostly (I would think).
Memory -- yes.

The solution?
- If you're going to keep the iMac, replace the bad graphics card.
or
- Look for a replacement Mac (again, might be the best way with an 8-year-old iMac).

 

[DeltaMac]

iMacs don't have that dual combination of a graphics card, plus integrated graphics.
Safe mode just uses the default video drivers, still using whatever graphics card is installed, but in a default graphics mode. The dual (switchable) video chips (graphics card + integrated graphics) from Apple is only on laptops from 2008 (and not on every laptop - 13-inch MBPros do not have the dual chips, only integrated graphics, some 15-inch also do not have dual graphics)
Anyway, safe mode does not use all of the graphics card memory, and works at a lower speed, so can still be a failing graphics card that might continue to work in Safe Boot mode.
And, as the OP has discovered, operating in Safe Boot mode is only a troubleshooting aid, and not a fix that allows you to work normally -- no graphics acceleration, and there's no audio (because the Safe Mode prevents other kinds of drivers from loading, as well)

 

[Fishrrman]

Thanks for the clarification, DeltaMac.
So... what is the solution?

 

[DeltaMac]

That iMac does not have a graphics "card" (that you can replace), the GPU is a chip on the logic board.
Not in a socket, either.
So, the solution, the fix, is replacing the logic board, I suppose.
And, that leaves the couple of options that you have already offered: Repair, or might be a simpler process to just replace the iMac.

 

[BritishB0xer]

That iMac does not have a graphics "card" (that you can replace), the GPU is a chip on the logic board.
Not in a socket, either.
So, the solution, the fix, is replacing the logic board, I suppose.
And, that leaves the couple of options that you have already offered: Repair, or might be a simpler process to just replace the iMac.

I got this imac used / refurbished, worked fine for a month, then got worse and worse after i erased the system it came with because it was a beta copy of BigSur.

maybe i can get the money back.
but are you sure your info applies to the 27” i7?
the specs describe mi imac to have an upgradable graphics card
Specs at this link

 

[DeltaMac]

"configurable" does not necessarily mean that there is a replaceable card.
In this case, the iMac has a GPU on the logic board, so configuring is done at the time of the original order (the logic board is manufactured with either graphics chip)
But, all you have to do is replace the graphics chip, I suppose. Buy the chip, replace the soldered chip, it's possible with the correct equipment and knowledge of circuit board repairs.

 

[BritishB0xer]

"configurable" does not necessarily mean that there is a replaceable card.
In this case, the iMac has a GPU on the logic board, so configuring is done at the time of the original order (the logic board is manufactured with either graphics chip)
But, all you have to do is replace the graphics chip, I suppose. Buy the chip, replace the soldered chip, it's possible with the correct equipment and knowledge of circuit board repairs.

Thats true, I guess i thought that because one can upgrade the 27 inch HD, Memory Graphics card, even Mother board as to the limitations of the 21 inch versions., and I just discovered that they are soldiered unto the mother boards https://www.ifixit.com/Answers/View/448377/change+the+graphics+card+in+my+iMac+27+(Mid-2017) since 2011