0
Score
Ben
85
Asked
Bad Display / Graphics Problem with iMac 24" 7300GT
Hello,
hoping someone can help me with this.
So I assumed the problem was a faulty video card (7300GT) so I bought a new one and fitted it, correctly as I've done this a few times before.
However I'm still getting weird artefacts on the screen, thinking about it they ar different to the ones you get with the GPU overheating/sol
See the attached screenshots (a combination of red and blue repeating patterns across the screen that redraw whenever you alter the display, i.e. move a window)
So, although not totally ruling out the video card I'm at a loss as to what the problem is.
1.New GPU hasn't helped
2.Artefacts appear on startup (Not software then?)
3.Don't appear to be heat related (SMCfancontrol makes little/no difference)
4. Known working LCD does not alleviate problems
5.Logic board in good superficial condition, I can't see any obvious problems.
6. RAM known working
7. Safe mode makes no difference
So hopefully someone can figure this out?
What I'm leaning towards is
1. Bad new video card?
2. Bad VRAM?
3. Bad GPU daughtercard?
4. Bad Logic board to GPU interface?
5. Bad logic board?
6. Power Issues?
7. LCD cable problem?
Many thanks in advance!
Update
Forgot screenshot...
1
Score
ABCellars
13.2k
Answered
Hook it up to an external monitor to help isolate the problem. If the artifacts are present on the external then the problem is hardware/video card related.
The 7300GT has a known issue with the capacitors on the card. The 7600GT was also an option for your iMac. They cost a bit more but you may consider it a cost effective repair vs the 7300gt loto.
ABCellars - He stated he replaced the GPU unit (could be used Vs new) so its hard to see both units having the same problem. I'll agree using an external display would isolate if the internal display and its' cabling were having problems. - Good idea!
Dan,
Yeah its a new GPU, however i put an old non working one in and it didn't display the red and blue artefacts. (it did display the usual symptoms of one of these cards gone bad and didn't boot properly) However its leading me to think that the new GPU is defective. Something also to note is that these didn't start appearing for roughly an hour after first putting it in, is it possible for a logic board to corrupt an otherwise good GPU? I don't have an external I can use at the moment, but I do have two LCDs and both exhibit the problems. Have examined and recleaned the logic board, unplugged everything apart from the essentials, even booted from firewire to see if the HDD was causing problems. Such an unusual problem though.
Ben,
Ben - I think ABCellars had a good idea using an external display. I would try that before going forward. If the external is OK it's the internal display or it's cable.
Dan,
Yeah worked fine on an external. Waiting for a new card. Gave me the opportunity to bump it up to the 7600GT though so not all bad. Will update once it arrives.
Ben,
0
Score
Dan
593
Answered
0
Score
Ben
85
Answered
Thanks,
Signal leakage as in electrical interference? or a faulty cable? I really don't think so, I used some iso alcohol on it but that wouldn't cause this would it?
In that case, would you suggest using different cable?
Some RF transmitter in the comp? should I unplug the wifi/bluetooth/
Update:
It also seems this guy had the same problem:
https://discussions.apple.com/thread/217...
It's the only other occurence I've found on the internet though!
You may want to re-wipe the areas you hit with Iso-alcohol. You may have left a film which is slightly conductive. The area to focus on is the video part of the logic bd and cabling for signal leakage (forget the WiFi etc...). Did you forget to re-install any shielding or could you have put the wrong screw into the logic bd so it's touching something?
Dan,