Imac Blue Screen Blues

[geezerpk]

Hardware: Imac 20’’, 2 GHz PowerPc G5, 2 GB DDR SDRAM, internal hard drve MATSHITADVD-R UJ-845
Operating System: OS 10.4.11
Serial # W85200D2SDZ

Yesterday I started the Imac and left the room while it was booting. When I returned a short time later, the only thing on the monitor was a screen full of background blue, a restart brought the system up normally. The computer operated normally for the next few hours, but after about 5-6 hours it stalled between images on the screen saver. Everything was dead, so I rebooted the system using the power button.

With this reboot the system came up with the normal gray screen/apple logo and went to the spinning progress indicator after about 30 seconds, about 30 seconds after this the screen went to the same solid blue and proceeded no further. No mouse no keyboard, no nothing. I tried several restarts, unplugged the power cord and restarted to clear the PMU. No luck. After about the 4th restart I let the blue screen remain in place for more than a couple of minutes. After about 3-4 minutes there was a slight shift in the blue color, and the arrow cursor appeared and the mouse was able to position the cursor. Of course there was nothing to position it over.

The computer will boot in Safe Mode, and Single User Mode, it will also boot from the Tiger installation disk. I booted in Single User Mode and ran Applejack in both the regular and deep cleaning modes. No dice. I also booted from the install disk and ran the Disk Utility which showed no errors, also corrected permissions from the Disk Utility.

I’ve restarted while holding down the p, r, option, command keys to clear PRAM and NVRAM.

I tried to run the Apple Hardware Diagnostics from the Tiger boot disk, and the first 3 tests came up normal. It seemed to stall out on the memory test. Documentation said the diagnostics should run from 5-15 minutes depending on hardware config — after 45 minutes, most of it during the memory testing, I gave up on it. Perhaps I lack patience.

While in Safe Mode, the Imac seems to operate fairly well, although I miss some of the features that Sale Mode cancels out, and it takes for ever to boot up.

The next step will to be to crack the case and reseat and rearrange the memory chips and check for bulging capacitors. I’d appreciate any additional suggestions and ideas that anyone might offer, hardware or software to try. Thanks in advance for any help.

 

[geezerpk]

Just an update that will perhaps others with a problem to the one I described in the original post, which has received no responses to date.

A discussion on another forum surmised that this problem is often caused by the onboard graphics card and/or the graphics ram. One of the responders suggested that the problem might go away if one removed all extensions beginning with the letters "ATI" from the "System/Library/Extensions" folder. Just move/copy the items to another safe location in case they're needed at a later time.

I did this, and it immediately solved the stuck blue screen issue. Apparently the ATI extensions enable certain graphics functions that speed up gaming, etc., but don't seem to have an effect on the applications I've run to this point. That's not to say that there might not be future issues. I suppose someone with enough patience could reload these extensions one at a time to see which one/ones cause the problems.

 

[eyoungren]

Just an update that will perhaps others with a problem to the one I described in the original post, which has received no responses to date.
A discussion on another forum surmised that this problem is often caused by the onboard graphics card and/or the graphics ram. One of the responders suggested that the problem might go away if one removed all extensions beginning with the letters "ATI" from the "System/Library/Extensions" folder. Just move/copy the items to another safe location in case they're needed at a later time.
I did this, and it immediately solved the stuck blue screen issue. Apparently the ATI extensions enable certain graphics functions that speed up gaming, etc., but don't seem to have an effect on the applications I've run to this point. That's not to say that there might not be future issues. I suppose someone with enough patience could reload these extensions one at a time to see which one/ones cause the problems.

That's a good clue. I had exactly the same blue screen problem with my old TiBook G4/400. But this only happened after my daughter sent it flying off the couch (she was two at the time).
Couldn't get it to boot correctly (same problem as you) so I stuck it away for awhile and bought my wife a new Mac (the old one was her's). Thought I'd try and fix it at a later point and found this solution as you did. While researching I also found a terminal command to prevent safe sleep, which was an issue for someone with an MBP that had the same symptoms (freezing when closing the lid). I found I could sleep the Mac before I closed the lid and then it'd be fine when I opened the lid again. But just closing the lid would cause it to freeze.
Ultimately I suspect that this is damage to the graphic chip on the logicboard. Pressure applied to the computer often kept it from freezing, but at a certain point it stopped doing any good. I finally replaced it with a 1GHZ TiBook which I gave to my son (my daughter got his iBook G3).
I've replaced the logicboard on this Mac once, but it just wasn't worth it the second time around. The case was breaking apart so I decided to just swap out the screen for the bad one on the TiBook I got my son.
Apparently when my daughter sent it flying it was on and the screen was active so I'm guessing the impact is what damaged the chip. The symptoms I describe above were the same ones I had when the previous logicboard went bad.
Hopefully this is not the case with your Mac, but I suppose it's a possibility.

 

[geezerpk]

Until I found the key to unlocking the blue screen freeze it was looking like a replacement Mac was on the horizon. It was looking more and more like a bad logic board, and with a 7+ year old computer, logic board replacement just wasn't something that made sense. Abandoning the PowerPC really didn't appeal to me very much. That would mean upgrading or replacing some fairly pricey apps like Photoshop, Illustrator, and InDesign. Ugh! These apps still run with decent speed on the G5, and my IMac does just about everything I wish to do dependably enough to suit me.