For the past several months I've noticed some weird color banding on my iMac. I don't remember when it appeared, and I don't recall anything triggering it.

It can be easily seem when displaying photos or video, but it is still there (albeit slightly) when looking at other things such as message boards or file windows.

Hopefully this is a software issue. If I play the same video in Quicktime and VLC, the window with VLC seems to have much less color banding (although it is still visible). However, the color banding doesn't go away if I change color profiles or brightness.


The culprit is a 2GHz iMac G5 running OSX 10.5.8. originally purchased in 2005.

The photo below (taken with my D40) shows the default background where you can easily see the issue (ignore the vertical artifacts that are a side effect of taking a photo of a screen). If you guys have any suggestions, I'm all ears.



[Edited on October 14, 2009 at 9:52 PM. Reason : ]

10/14/2009 9:51:18 PM

Its a hardware issue. iMac G5's are absolutely infamous for bad capacitors on the logic board. They ALL go bad eventually, sometimes slowly and sometimes not. Color banding and/or display flickering is a classic sign, and it'll go downhill from there. Honestly, you're lucky it lasted so long. Half the caps are on the power supply rail for the onboard video, so what you're seeing is caused by improper voltage and ripple to the GPU.

The only way to fix it is to pull out the logic board and manually desolder all 20-some bad capacitors and solder in new ones. Or buy a new logic board at $500-600. I've done about a dozen of them that I've bought as broken off Craigslist as broken and they're perfect after the repair. If I were to do it as a service it wouldn't be cheap, like $150-200 range. I think there are places you can ship the board that will do the repair, too.


Easy way to verify it is to pop it open and look at the caps. Its super easy to open, just lay it screen down and turn the three screws at the base, then lift the back lid off. There will probably be at least a few caps that are bulging or leaking.

10/14/2009 11:13:29 PM

Thanks for the info! I googled it and found what looks to be a decent guide to replacing the capacitors.

http://jimwarholic.com/2008/07/how-to-repair-apple-imac-g5.php


I will have to open it up later tonight and see if any of the capacitors are bulging or leaking.

edit: I suppose I'll also mention that I had my PSU go bad awhile back. The computer just started to randomly cut off with no warning. I took it in and had it replaced as I waited, under warranty. I wonder if the two are related. This was probably 2 years ago, though.

[Edited on October 15, 2009 at 10:17 AM. Reason : ]

10/15/2009 10:15:31 AM

The PSU and logic board both had bad capacitors in some models, and for a while there was a warranty extension on those models. Before you take it apart yourself, it may be worth calling Apple to see if there are any extensions still going on and if your computer would be covered, especially if they already had to do the PSU.

10/15/2009 2:19:45 PM

Looks like I might be back at Square 1.

I took the back of my iMac off a few minutes ago to look at the capacitors, and I didn't see any obvious bulging/leaking/exploding.

I have a friend who said he would be willing to help me put new capacitors on if need be (he teaches mil-spec soldering) so I might take him up on that anyway.

On a slightly different note...
My wife's Macbook is actually having wireless issues (doesn't want to connect unless the router/access point is practically next to the computer). I am considering taking both computers to the Apple Store to see what they can do...

10/15/2009 7:39:46 PM

what is there to teach for mil-spec soldering? Just use a damn scope, be careful, and be on your way... Takes about a day or two to learn on the job. I learned it my first week of co-oping with no fancy schmancy teachers.

10/15/2009 8:41:14 PM

do you want a cookie?

10/15/2009 10:20:29 PM