iMac G4 flat screen GUI streaks

[Danny Dorko]

Can you help me nail this (hardware?) problem?

iMac G4 1GHz OS X 10.4.6

As the machine warms up the screen starts to show vertical streaks where windows or graphics refresh or move. If I continue using it, it will crash.

Under the same circumstances, if I don't use the screen (say, working over Airport) the machine will stay up forever.

In target disc mode the machine stays up (and the Firewire screen works forever without breaking up).

The iMac hardware test disc shows no problems (and the test screen works forever).

It's just the OS X GUI that breaks up and crashes.

I have scrubbed and reloaded OS X from scratch. The problem persists.

Any ideas where the fault is?

Thanks for reading...

 

[Benjamindaines]

Hmm... This sounds like your graphics card is going bad. I don't know why it only does it under OS X, but my theory is that its something to do with all the other things that work fine (target mode, software test) don't use OpenGL or Core Imaging. If you are still under warrantee I would take the iMac to an Apple store and get it checked out, if you aren't under warrantee then perhaps consider a new machine (repairs will cost more then the iMac is worth).

 

[neocell]

Stupid, stupid me
Didn't completely read before posting
please delete

 

[FocusAndEarnIt]

I don't think there is anything you can do unless you want to replace the motherboard (where the graphic card relies)

 

[Danny Dorko]

Thanks Benjamin... it's way out of warranty, but you're confirming my thoughts.

I was wondering if there might be a DIY fix, because like you say a shop repair is probably uneconomic. But maybe it's curtains.

No probs Neo, I was baffled when the video tests came up clean. I guess it's intermittent.

The mother board isn't cheap Stewart?

 

[Benjamindaines]

No probs Neo, I was baffled when the video tests came up clean. I guess it's intermittent.

The mother board isn't cheap Stewart?

One more thing I've thought if is can it work fine with an external display rather then the internal one? And the only logic boards you will find will be on eBay so prices vary, you could get a new one but it's up to you whether you want to deal with eBayers.

 

[FocusAndEarnIt]

Thanks Benjamin... it's way out of warranty, but you're confirming my thoughts.

I was wondering if there might be a DIY fix, because like you say a shop repair is probably uneconomic. But maybe it's curtains.

No probs Neo, I was baffled when the video tests came up clean. I guess it's intermittent.

The mother board isn't cheap Stewart?

Nope, not at all.

It contains the processor, graphics, USB, audio, etc etc and so it's very expensive.

It's matt, btw.

 

[Danny Dorko]

Yep, I thought so. Thanks guys... and sorry Matt - you crazy guys with your crazy names, eh?

 

[mkrishnan]

Mmm, but didn't you say that when you boot off a system restore DVD, you see no disturbances in the screen while you're in the test software? That strikes me as strange, if this were a motherboard failure....

 

[Danny Dorko]

Mmm, but didn't you say that when you boot off a system restore DVD, you see no disturbances in the screen while you're in the test software? That strikes me as strange, if this were a motherboard failure....

Not the restore DVD... the iMac H/W Test CD. I didn't know I could boot off the DVD... I might give that a go.

It does baffle me that the test CD and target disc mode screens are rock solid and it's only a screen with the OS X GUI that breaks up.

I was wondering about running Unix from the CLI but I think that's in an OS window?