> On Aug 4, 2016, at 5:19 PM, Al Poulin <[email protected]> wrote: > > Greetings, > > Am I looking at a hardware problem or misbehaving software? > > My workhorse is the last 24 inch iMac that Apple produced. Running 10.9.5 > Mavericks. > Early 2009 “Display Port” > 2.66GHz Intel Core 2 Duo > 4GB RAM > 640GB HD > SuperDrive > NVIDIA GeForce 9400M graphics with 256MB of shared DDR3 memory > > When waking from sleep, occasionally the display will scramble for about 5 or > 10 seconds before organizing itself. This seems to happen more when multiple > screens are left open, even as few as three. Or, it may go black for a few > seconds and then settle down. There are 30 to 35 items on the Desktop. > > This has been happening for two or three years, but seems to be more often > now. > > If this is hardware, should I eventualIy expect total failure of the screen > to display properly and prevent access to the system? > > Thanks, > Al Poulin
Al, iMacs of that vintage and screen size tend to develop issues with the video card, which is plugged into a slot on the logic board and has a finned heat sink with lots of piping. The card and heat sink sit at the bottom of the logic board and are directly above the air intake vents at the bottom of the case. Since the video chip itself is attached to the card with hundreds of little solder dots (the notorious BGA or ball grid array), any overheating of the card or chip can cause one of more of those solder joints to weaken and/or crack. Thus any accumulation of dust or dust bunnies that blocks the cooling fins can be bad news for the BGA and thus video performance. The finned heat sink for the cpu is directly above the video card heat sink, so there’s an impact on the cpu also if there’s blockage. I have seen exactly the pixelization you describe as scrambling in video cards that ultimately fail after many heat up/cool down cycles. The problem is accelerated dramatically by dust buildup blockages of the cooling fins. So, yes, I believe you are experiencing the symptoms of a failing video card. You can open the case, disassemble things enough to clean out the dust. But the damage won’t be reversed, although failure may be delayed by the cleaning. The good news is that the card can be replaced. The bad news is that new cards are hard to find and pricey. Used cards also can be hard to find and equally pricey, and there’s no guarantee that they won’t soon fail too. I have used a couple of repair services advertised on eBay, with mixed results. Reflowing the solder joints is a standard approach, and often restores a card to working order. However, internal arcing causes damage and a reflowed chip quite often fails again, for good. Thus I no longer ask for a reflow. Rather, I pay a few more dollars (@ $150 or so) and get a brand new video chip installed. New chips come complete with the BGA solder balls, which makes removal or the old chip and installation of a new one a breeze for someone with a high end work station and the training and experience. However, it’s getting more and more difficult to find a repair service that has the proper replacement chips. So you’ll have to do a lot of digging to find a vendor who not only has the correct video chip for your Late 2009 A1225 24” iMac, but also is willing to do the repair on a card that’s already exhibiting symptoms. Go into About This Mac and determine exactly which of the three video cards available in your model has been installed. Then go looking for a vendor who has that chip in stock and will install it. I have found eBay vendor/seller brickfence (he’s in the L.A. area) to be highly reliable, honest and easy to deal with during multiple transactions over several years. But there are lots of others, so do careful shopping and check their feedback. Jim Scott Eureka, CA -- You received this message because you are a member of the iMac Group, a group for those using Apple iMacs and eMacs. The list FAQ is at http://lowendmac.com/imac/list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To leave this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/imaclist --- You received this message because you are subscribed to the Google Groups "iMac Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
