Place to buy iMac G5 lower (CPU) fans
Digi-Key (
www.digikey.com) has fans with the same Delta part number as is on the label on Apple's fan (BFB0612H) (Digi-Key's part number is 603-1117D), but the picture of the housing, at:
http://dkc3.digikey.com/PDF/T072/2008-2009.pdf
...looks different. I haven't ordered any of these to see if the fan is transferrable to Apple's housing, but I may soon; if I do, I'll report here. Digi-Key sells them for $12.85. Order page for this fan is at:
http://www.digikey.com/scripts/DkSearch/dksus.dll?KeywordSearch
If you do a search for Digi-Key's part number on their web site, for some reason it won't come up, so use Delta's part number.
Companies that may sell the actual Apple fan and its special Apple housing (beware that some may have outrageous prices--check all these companies for the best price):
www.applepalace.com
www.dvwarehouse.com
www.macresq.com
www.macsupportstore.com
www.preowned.com
And, of course, eBay.
I just spent way too much time trying to quiet a buzzing, rattling iMac G5 ALS 17" CPU fan, by taking it apart and trying to remove a spring below the lower bearing, as someone named David Craig recommends on the Macintouch web site, but I found it impossible to remove the lower bearing and hence the spring under it. I oiled both bearings with a special oil called Bel-Ray, but it didn't help. Next step: buy a fan from Digi-Key and see if I can graft it into Apple's fan housing. If it can't be grafted, next step is to buy a fan from one of the companies above, or maybe from Apple if they have them in stock when I want to order one, and cross my fingers that it's quieter than the one I'm replacing.
Daveway: the difficulty in removing the CPU fan in the iMac G5s that you've seen, where you had to remove the logic board first, is probably due to the difference between the 17" and the 20" models. The post by Eldorian above shows the removal process for the 17" model. I haven't tried this in a 20" model, but looking at the Apple Service Source instructions, it does say you need to remove the midplane first, which includes the logic board.
I also just spent way too much time trying other approaches to cool the overheating, noisy iMac G5 17" ALS that contained the fan I mention above, and thus try make the CPU fan run slower and so quieter, but nothing worked. I had an identical model in my shop at the same time, and ran the same applications, web pages, etc., and it didn't overheat or spin its fan too fast--it ran quiet under all the same circumstances. Here are some of the things I tried, which work for some of these Macs, but not most:
- Reset the SMU (first, of course)
- Changed the Energy Saver settings between Reduced, Automatic, and High. High just made the CPU hotter and made the fan run too much, not enough extra to compensate for the extra CPU heating. Automatic was the default, where the fan noise problem was audible. Reduced kept the processor cooler a significant amount of the time, but still, doing anything to raise processor usage, even having just Dashboard open, and two Safari windows open, one with a CNN web page with a couple animated ads, and one at the YouTube home page, caused the fan to run too fast, even when the CPU temperature (I used the iStat Pro widget) was reported to be at the threshold level of 148 F, past which the CPU fan starts to rev up above its default of 1500 RPM. The fan in the iMac I was working on, stayed between around 2940 RPM and 3600 RPM with these web pages open.
- A known-good installation of OS X, from two other startup drives. Some people report reinstalling OS X helps, but it wouldn't have here.
- Some people report installing a matched RAM pair, but this iMac already had that.
- Pointing a fan at the rear of the iMac, so that it was cool to the touch--CPU still got too hot.
- The known-good power supply, and CPU fan, from the other, good iMac I had in the shop.
- Installing a gasket along the bottom of the CPU fan's opening to prevent it from drawing in warm air from the inside of the Mac--normally there's a gap between the fan housing and the grille along the bottom of the Mac where it pulls in air from the outside world, and some warm air from inside the Mac could get into the fan that way.
- Moved the hard drive's temperature sensor to sit right on the body of the drive, instead of along the side, on a bracket that wraps around the drive--this had no effect on measured drive temperature. I was hoping it would be seen as hotter, and thus spin up the hard drive fan more, cooling the hard drive a little, and thus the CPU heat sink, which is directly below the hard drive.
- Replaced parts on the logic board that seem to be the CPU's temperature-sensing devices. The "CPU T-Diode" seems to actually be a chain of three LMV2011 op amps (used for many purposes in electronics, including temperature sensing), near the lower right corner of the logic board, between the lower RAM socket and the heat sink. These are small, 5-legged parts (3 legs on one side, two legs on the other) marked U3601, U3602, and U3603 on the logic board, and marked "A84A" on the parts themselves. National Semiconductor is one manufacturer (maybe the only one). I found these parts by heating various likely parts on the logic board with the tip of a soldering iron, until I heated parts that caused iStat to report that the CPU temperature was rising, and the fan speed rose; when I cooled them with a can of compressed air, the reported CPU temp, and fan speed, dropped quickly. There's another part nearby, under the edge of the heat sink, that uses the same package, marked on the logic board as VR3100, but heating and cooling it didn't produce nearly the effect of cooling the other three parts. It's possible the actual temperature sensor is elsewhere, even in the CPU itself--I think one is inside the CPU, but either Apple isn't using it, or the CPU they used doesn't contain one--and so maybe the current/voltage delivered by this other theoretical sensor passes through the three op amps, and so any heating of these op amps could change the perceived temperature, but these op amps are supposed to be a type that, when in the proper circuit, are relatively immune to temperature change, which makes me think they're in a circuit that turns them into temperature sensors.
I tried several other things, but nothing helped this Mac. I wondered if installing a cooler-running hard drive might help, but my feel of things from the above work, was that the CPU has a very localized overheating problem, and was simply getting hotter than it should, and nothing would help short of directing air right on top of the heat sink, with the rear cover removed (not too practical for everyday use), or an add-on external fan stuck to the rear cover, at the spot where the CPU fan's air exits (not the slot at the top of the rear cover), pulling more air out of the Mac through holes drilled in the rear cover. I didn't try this, since it's not my Mac. My client may go for it though, but he originally wanted a logic board exchange--I was trying to discourage him from that, since a replacement board might not be any better, since Apple uses the same stock of parts for repairs as they do for manufacturing the complete Mac, and of course a similar percentage of those boards have overheating problems, as are iMac G5s with these problems. I also had a feel from working on this Mac, that some (including this one) may have two or more problems contributing to the CPU fan running too fast too much of the time: besides outright processor overheating, the SMU in some logic boards may misinterpret the data from the temperature sensors; or the delay time (hysterisis) built into the SMU and/or the fan speed control circuit that's supposed to slow down the fan after the CPU has cooled, doesn't always work properly.
