Coloured lines on second screen (Not sure if hardware/software)

[Mewier]

These lines have an about 50% chance of showing up after my iMac boots. If I restart my computer 1-3 times it will go back to normal, which is odd.
The lines slowly wobble. I've searched and found other problems with odd colors, but nothing similar to this.
My iMac is an late 2012 model, 10.8.4 2.9 GHz Intel Core i5.

Help is appreciated.

 

[macthefork]

Have you checked the cable? Sounds like it could be a loose or bad cable.

 

[rkaufmann87]

These lines have an about 50% chance of showing up after my iMac boots. If I restart my computer 1-3 times it will go back to normal, which is odd.
The lines slowly wobble. I've searched and found other problems with odd colors, but nothing similar to this.
My iMac is an late 2012 model, 10.8.4 2.9 GHz Intel Core i5.

Help is appreciated.

If the cable checks out OK (replace it) then run Apple Hardware Test in extended mode 2-3 times. If it is hardware then you will need to take it in for warranty service.

 

[Bear]

Have you checked the cable? Sounds like it could be a loose or bad cable.

Check not only the cable, but also check the connector on the display. Also, do you have something else you check the display on. Especially using the same connector on the display.

It could be the iMac, the cable, or the display itself.

 

[Mewier]

Thanks for the replies! I did the test and it didn't find anything.
I checked the VGA cable and noticed that the end that goes into the screen has only one functioning screw, while the other one won't go in. Can this be the problem? Or shouldn't that cause the problem to happen every time?

 

[macthefork]

VGA? That iMac has a Mini Display Port (Thunderbolt Port). Are you using an adapter and additional cable?

If the finger screws can't be tightened or even go in it's probably a bad or damaged connector right there. Check closely that no pins are bent on that connector cable.

 

[sallsyn]

great.do you have something else you check the display on. Especially using the same connector on the display.

 

[Mewier]

Yes, I am using an adapter.
This is occurring less frequently now, but I'll try switching the vga cable out.