[Plant7575]

I have an iMac G5 running OS X 10.3.9. Occassionally, the computer will suddenly draw two superimposed screen images, offset horizontally by a few millimeters, then freeze. After about 5-10 seconds, the screen unfreezes, displays just one perfect screen image, and returns control of the computer to me, with no loss of data or information.

This began about about a month or two ago. At first it happened rarely, but it has been happening more and more frequently lately -- now up to about 1-2 times a day.

In addition, there is a more severe, likely related problem, which has happened only three times. The computer will suddenly freeze and displays only a regular pattern of black dots on a white screen. The only way out of this problem is to pull the plug, replug, then reboot. This has happened only three times so far, once about a week ago, then yesterday, then again today.

Something is gradually getting worse. I suspect a hardware problem, but this is a very uneducated guess (I no very little about hardware.)

I ran the TechTool Deluxe disk that came with the Applecare Protection Plan. The computer passes all tests (except the Surface Test, which was skipped, as is the default setup on this diagnostic disk).

I called Apple. The first person said there were a couple of things that I could try. The first was to reset the PRAM, which I did. When the problem continued, I called again. Unfortunatly, the second person had no clue as to what other things to suggest. Her only suggestion was to take it into a service rep. The nearest service rep is over 2 hours away, and it is hard for me to get off work to take it there on the weekdays.

Has anybody else ever seen this? Anybody have any ideas what may be causing this, and what I could do about it?

Thanks.

[killertofu]

Two things it could possibly be, software or hardware, obviously.

If it is a software problem, I would have to guess that it has something to do with your computer running Expose. If this is the problem, the easiest way to solve it would be to clean reinstall OSX.

If it is a hardware problem, you could be having trouble with your video card. From what you describe it sounds like it could be that the RAM on your video card is having problems and your best bet would be to replace it.

If you want, backup your stuff, and do a clean install. Then see if the problem persists. If it still happens after you do a clean install, then at least you know its not a software problem. If it doesn't happen anymore. Then it may have been an after-purchase program that you added somewhere down the line.

Either way, it might be more worth your time to take it in somewhere else. I know it's two hours away, but isn't that better than spending money on a guess?

[Plant7575]

Thanks for the response.

I have been watching more carefully and now know more about this problem. I am referring here to the temporary screen freeze with the double image, (The rarer total lock-up has not happened again, yet.)

It appears that this problem only happens when waking the computer up from sleep, usually about 30 sec to 1 min after waking the computer up. At least once, it happened twice, the second one coming maybe a minute after the first, It does not always happen after waking from sleep. Once, I forced the computer to sleep, then woke it up right away -- no problem. Perhaps the computer needs to be asleep for a longer time to make this happen??

Any ideas?

[Plant7575]

Well, the problem got a lot worse (computer began freezing up on restart), but it has been fixed. It turned out to be bad capacitors on the logic board. The whole logic board had to be replaced. Fortunately I got the AppleCare extended warranty.

But it turns out that, according to the local guy who did the warranty work, that this is a known problem, and Apple has quietly extended the guarantee (just for this problem) on some of the Imac G5s (depending on the serial number) for (I think he said) two years. Don't quote me on this, but if you've got a similar problem, check into it.

But when I called the AppleCare support number, they had me try all kind of other things before admitting that I had to take it in for diagnosis. They sent me a new inverter board to install and had me reinstall my system software. One of the last guys that I talked to at Apple did ask me if I had noticed any bulging capacitors when I replaced the inverter board -- so at least he was aware of the problem.

When I took it in for service, the repair person immediately guessed the problem (he has seen a number of them). He opened it up, and sure enough, several of the capacitors were bulging at the top.