GPU/display issue?

Hi Mike

Unfortunately the disc is not with me at the moment. Given that the machine is now running Mavericks, I am unsure as to whether the disc based version of AHT would work, or whether the OS on the machine has to be the same as the OS on the install disc that contains AHT? Anyway, I tried running AHT by holding D at start up and only got as far as the apple logo and check pattern ie AHT did not appear and the machine did not boot.

Thanks

Col

Porkpies1999 - it just stays with the checks and logo. Only goes black in the sense of the display eventually sleeping (I think), which again suggests a sort of boot in the background as it must be engaging some sort of energy saver preferences.

Thanks

Col

Tammy - I'll be fascinated to see what hardware tests come back with.

Andy

Thanks for your input - I've now disabled quartz, to no apparent effect. I searched for the extension removal threads and followed instructions for loading extensions while in safe mode.

This revealed that 192 extensions failed to load, with only 46 seeming OK. The ones that failed were pretty wide ranging - certainly not all graphics related. I copied the 192 and removed them from the extensions folder and tried to reboot: kernel panic, system unable to find driver and unable to perform a kext scan. Won't now boot in safe mode. Luckily it's a Mavericks system as I have no install DVD but I do have a Time Machine back up, so currently doing a full system restore. Will be a bit more cautious with extension removal next time!

BTW, the bands/stripes are still there even as I am doing the system restore and the checkerboard pattern was there even as the machine refused to boot at all. I'm guessing that means it is definitely hardware, so I just need to narrow it down to the GPU rather than full logic board and find the extensions that are preventing a normal boot. Either way, the machine is unusable with the screen in its current state, so its probably all a bit pointless now.

Cheers

Col

UPDATE:

System successfully restored from back up. I restored from a back up taken the day before the problems started, just in case something was done that caused the issue. That has made no difference: still can't normal boot, but safe boot worked. While safe booted, I have now removed the various ATI related extensions and I am now able to boot normally. There is defnitiely still a serious problem, but the screen pattern is now different - stripes all over rather than confined to the bands, but a bit more transparent:

Still not exactly usable, as the visible strips on this pic dance about and there are lots of single pixel wide lines in between. Still, it looks like some sort of progress, so I'll keep experimenting with graphics related extensions.

Hi Tammy (and anyone else who can help)

That's good news. Things at my end have gone a little strange. I put back all the extensions one by one and was able to boot nromally, even once all of them were back. I did however get a message that the ATI 2600 extension wasn't installed properly, but as it was still booting and I couldn't see any way to reinstall it (other than just popping it back in the extensions folder) I moved on. The screen was getting a bit worse, but still just striped rather than banded.

Having read further threads on similar problems, I decided to take the whole thing apart (great ifixit step by step guide). Nothing seemed amiss - all connections seemed secure, no obvious burnouts. Removed a LOT of dust and put everything back together again.

The machine started straight up when I plugged the power cord back in (I didn't get a chance to press the power button) - the screen flashed briefly round the edges and then stayed black. No stripes, no bands, no image.

I could hear the hard drive spinning, so pressed some buttons on the keyboard and got a warning tone, suggesting some sort of boot. I forced shut down and restarted and then tried to log in with the screen still blank. The bad news is that the screen has stayed black since then. The good news is I now have full remote access and can even screen share. The screen now has no bands when I screen share - I can see and interact with the full screen as normal and have managed to retrieve files etc over the network.

I am still deciding whether to order a new (second hand) video card. Looking in system profiler to get info on this it now shows no info AT ALL under graphics/display and in the 'more info' tab from the apple menu 'about this mac' version of system info it now says "No display detected". I am now unsure whether I have somehow 'blown' the display (I still get a brief white margin round the screen on start up) or whether both graphics card and screen are both goosed, or whether I should take it apart again to make sure the display itself is properly connected. If the graphics card was fubar, would I be able to see anything at all via screen sharing? I don't have an external display I can test it with. I don't want to fork out for GPU only to find it is the display.

Any views on next steps?

Col