On May 6, 2014, at 9:19 AM, lrbarrios <[email protected]> wrote:
> I have an iMac G5 that has a couple strange problems. The problem has been > happening ever since I got it from my company about 3 years ago. While it > was at the office, I know it had been taken into the shop a number of times > for some work (don't know exact what the issue was). I do know that they > replaced the motherboard and the hard drive. All that said, here's the > issue... If I let it sit idle, the screensaver will kick in and work fine. > Eventually, the screen will go black and the system will go to sleep. I can > see the power light slowly pulsing. Everything is fine. When I return to > the computer, I press the Shift key to wake up the system. It responds by > making some 'hey I'm waking up noises' (e.g. hard drive spinning up, perhaps) > and the power light stops pulsing. This is where it all goes south. The > screen never returns. It stays black. Then, the grand finale... The system > fan kicks into very high gear. The system will stay in this state until I > press and hold the power button to turn it off. It's a bit of an > inconvenience when this happens, but it's not a show-stopper. Or is it? > This is what happens next. I press the power button to turn the system back > on. It goes through it little screen flashes and wipes and eventually the > Apple logo appears. IF the little spinny thing appears under the logo, all > is good and the system will boot normally. If it doesn't appear, the next > float in this parade is a kernel panic error screen. If I turn it off and > back on, it'll probably do it again. If I turn it off and let it sit for at > least 15 minutes, it'll probably work normally. > > Every once in a while, I get the kernel panic screen out of the blue. > YouTube and Craigslist seem to give it fits for some reason. Any ideas? Lonnie, Steve Jobs once defended Apple's decision not to offer Blu-Ray drives because they are "a bag of hurt." Unfortunately, so were and are the vast majority of G5 iMacs. The symptoms you describe are quite common. I had a 20" first-gen G5 iMac on my workbench last week with the same issues as yours. Most of the problems are related to bad capacitors. Apple and most other electronics manufacturers bought capacitors from an Asian firm in the early 2000s. Turned out the manufacturer used a stolen electrolyte recipe which was missing a key ingredient that stabilized the electrolyte and prevented it from boiling and thus losing the ability to perform its task of holding current values. From a few months after going into service until today, those capacitors have been failing. Sometimes they explode; sometimes they vent out the top or bottom; sometimes they look OK but aren't. Whichever it is, a failing or failed capacitor cannot maintain correct electrical values. When this happens, the dozen or so capacitors in the G5 iMac's power supply and the two dozen or so on the logic board can cause all sorts of symptoms, most of which you now know intimately. Add to this bad capacitor issue poor thermal management. The iMac G5 power supply is at the bottom of the case, where half of the incoming cooling air must pass through it. This results in heated air washing over most of the capacitors on the logic board, further exacerbating the capacitor issue. There are only three temperature sensors on the logic board, which control the optical drive, the hard drive, and the video/cpu/bridge chip fans. (My late-2012 27" iMac has 18 thermal sensors.) The fan that blows incoming cooling air through the copper fins atop the huge heat sink over the bridge, G5 cpu and graphics chip sucks air from the bottom of the case, much like a vacuum cleaner, and thus results in the fan and the cooling fins getting plugged up with dust, lint, etc. As I said, poor thermal management. Fortunately, Apple remedied most of these thermal management issues in the third-gen white iSight G5 iMac, and continues to do so with each new generation of iMac. Another issue that arises in G5 iMacs that have seen plenty of overheating will be familiar to G3 iBook owners: broken solder joints in the BGA (ball grid array) that affixes the video chip to the logic board. Your main problem is a failing logic board. Apple replaced those back in the day, but that program closed years ago. I've even seen capacitor failures on some of those replacement boards. And because G5 iMac logic boards are multi-layer, I've seen non-professional cap replacement attempts permanently damage the boards. This is primarily because Apple began using high-temp unleaded solder on G5 iMac boards, and hand-held soldering tools cannot reach the proper temperatures to desolder and resolder the capacitor legs properly. It is possible to replace the bad caps and reflow the video chip BGA, etc. professionally, but it's not worth the time or expense, in my judgement. Better yet, migrate your data to an Intel iMac. Early 2006 and newer Intel iMacs are much better machines, and their prices are quite reasonable. But avoid 17" Intel iMacs (most have or will have bad LCDs), and be quite leery of any 24" Intel iMac (BGA failures of video chips on daughterboards). Hope this helps. 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. 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