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InfoTime

macrumors 6502
Original poster
Jul 17, 2002
478
242
Just upgraded machine by replacing internal hard drive with an SSD and added more memory. Everything works great except there's a very minor, mild flickering of the screen.

The whole screen flashes. It's almost imperceptible. And it doesn't do it consistently or predictably. Sometimes I'll look over at it and think it's gone away, but if I stare at it long enough I'll see it.

I may have damaged the display cable when I opened the machine. As I was carefully lifting up the display and removed or removing the vertical sync cable the display data cable popped loose.

I also may have bent the cable by flexing it too much when putting it all back together. It was difficult getting that connector seated. It's not damaged, but it's just in a difficult spot.

The symptoms lead me to suspect a problem with the backlighting. But I wonder if it's the display data cable, since I'm afraid I might have damaged something - either the connections or kinked the cable..

I've gone back in to the machine and disconnected and re-seated all three cables - the vertical sync, the data display and the LED backlight power cables. The issue persists.

Any suggestions?
 

RichMilo

macrumors newbie
May 31, 2013
6
0
Like an old TV set, just give it a hard slap on the side til the picture is good ;)

In seriousness tho I just had the same problem upgrading my brothers Mac, and am going to look at it tonight. I'll let you know if we get it sorted out.

Rich
 

InfoTime

macrumors 6502
Original poster
Jul 17, 2002
478
242
Be interested to see what you find. I ordered a new display data cable. Hopefully that's all that it is. I may have damaged the connector and / or kinked the cable to cause this.
 

strukt

macrumors regular
Aug 8, 2012
119
118
Norway
The connector is very fragile so you should be aware of that when working inside the iMac. Also make sure you flip the locking lever up... thats pretty important too.

Lets hope its just the cable though, crossing fingers! ;)

If all cables are okay and you still get flickering it could be the backlight/inverter board on top left.
 

InfoTime

macrumors 6502
Original poster
Jul 17, 2002
478
242
If it's a 27" iMac, take it to the Apple Store to get it checked out...

My iMac fell culprit to the video card failing and it was replaced free of charge within a week...
Were you outside the warranty period? What model year iMac? Is it a well documented recall?
 

kepler20b

macrumors 6502
Oct 18, 2014
473
401
you should be sure that your cables are seated properly.

I'd open it back up and reseat them. Also i'd remove the new ram and try to pinpoint the issue.
 

Walde

macrumors newbie
Jan 3, 2016
2
0
a bit late, but for those who have the same problem:

There are 4 cables. When the screen is light flickering, you have forgotten to reconnect the thin cable with the two pins on the upper left side (for the imac 21.5 middle 2011)

sorry for the bad english....
 

Walde

macrumors newbie
Jan 3, 2016
2
0
a bit late, but for those who have the same problem:

There are 4 cables. When the screen is light flickering, you have forgotten to reconnect the thin cable with the two pins on the upper left side (for the imac 21.5 middle 2011)

sorry for the bad english....
 

InfoTime

macrumors 6502
Original poster
Jul 17, 2002
478
242
I installed a new replacement display cable. Problem solved.

I think the original cable must have gotten crushed or twisted or bent somehow. It wasn't nice and flat like the new one.
 
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