iMac 2011 27" black screen

[insydney]

2011 27" iMac 1312 black screen issue
i just acquired this 1312 iMac which has black screen issue.
on power up the internal screen works at a very low 'brightness' F1 setting, i.e. you can hardly see it on the internal screen, but whenever you raise 'Brightness' above 2 the internal screen goes black.
you CAN however see it clearly on an external monitor
if you put the system to 'sleep' the inbuilt screen will come back, until you raise the brightness again
it appears these 27" screens had many issues in the past that i am just learning about
so what should i look at first ?
something that may be pertinent is a previous owner added an SSD to the original HD, so it has both drives now.
is there anything i should look for regarding temp sensors which might produce this result ?
cheers

 

[nathansz]

2011 27" iMac 1312 black screen issue
i just acquired this 1312 iMac which has black screen issue.
on power up the internal screen works at a very low 'brightness' F1 setting, i.e. you can hardly see it on the internal screen, but whenever you raise 'Brightness' above 2 the internal screen goes black.
you CAN however see it clearly on an external monitor
if you put the system to 'sleep' the inbuilt screen will come back, until you raise the brightness again
it appears these 27" screens had many issues in the past that i am just learning about
so what should i look at first ?
something that may be pertinent is a previous owner added an SSD to the original HD, so it has both drives now.
is there anything i should look for regarding temp sensors which might produce this result ?
cheers

I had a similar problem to this for awhile on the same model that I bought used. I could have the brightness higher than 2 but it would often go black. turning off "automatically adjust brightness" made it happen less but would still happen sometimes

I remember reading it could be caused by the screen not sitting properly in the chasis

the problem went away for me after I replaced the original ssd and upgraded the graphics card but I suspect that is just because I took everything apart and put everything back together again rather than having to do with the graphics card itself

when I took it apart it turned out that the wifi antennas weren't connected to the board either so someone had obviously been inside it previously, and perhaps not put everything together quite right

 

[insydney]

iMacs are yet another steep learning curve to me, i've had several MacBooks over the yrs, after a friend (questionable) lured me away from pc's with a gifted macbook. i was sucked in by the 'quality' and foolishly believed it. over the yrs it's been a constant stream of catch-up and high maintenance
so i decided to try the big brother, the iMac cos the screens looked impressive, now i'm back on the 'issues' later, on the bottom rung. i wish i had done more background research
i must be a masochist however in a weird way it's an interesting battle, although it's dragging me away from more important issues

so i'll take a deep breath and look inside i guess.. at the very least a good clean and new thermal paste won't hurt

 

[jsusa]

It seems to be just connection problem, you will have surely open and pull the motherboard out then connect firmly everything together back, then you will be more clever. I did bake graphics, changed the ssd, hdd removed all ssd and put just one ssd connected to odd connector and nothing changed, but when I opened it, reconnect everything and turn it on it came back.
Cheers