Amongst the TidBITS staff, I'm a bit of an anachronism: my main Mac is an ever-aging Power Mac G4 Quicksilver I bought (cheap!) in early 2002. The machine originally shipped with dual 800 MHz processors, and last year I installed a Sonnet Encore/ST G4 Duet processor upgrade, taking the CPUs to 1.27 MHz. (See TidBITS-754 for a review.) I currently have no plans to replace the machine, since I regularly use professional audio software which can't run under Classic and hasn't made it to Mac OS X.
However, the QuickSilver has had one problem since they day I bought it: it's loud. Later I realized - and thanked my lucky stars! - it wasn't nearly as loud as the Mirrored Drive Door G4s (the so-called "Windtunnel" G4s) that replaced it in Apple's product lineup. Apple eventually instituted a power supply replacement program for the Mirrored Drive Door models to quiet them down, but those machines are still an industry-leading example of cacophonous computing. [Speaking as an owner of one of the aforementioned Power Macs, I can say with some assurance, "Eh? What was that?" -Adam] However, no such noise-dampening replacements were made available for my system, and I just counted myself lucky the sound was tolerable most of the time.
A Harley Under the Hood -- Things changed in mid-2004 when the QuickSilver began emitting an occasional loud, vibrating hum. The first time, I admit I gently kicked the machine: that solid bump seemed to make the sound go away. But over the next few weeks the new noise gradually became both louder and more frequent, and I noticed it seemed to happen during heavy processor loads or during days my office was particularly warm. I figured my Mac had developed some sort of vibration problem when one fan or another kicked into high gear to dissipate heat. But the Mac lives under my desk, so isolating the cause meant crawling around and probably running the machine for a long while with its case open: that might delight my cats, but wouldn't be a good idea in general. Loud and annoying as the new sound was, I let things be.
Last year while I was reviewing the Sonnet CPU upgrade, I once happened to be under my desk when the loud, vibrating noise started up. Ah ha! From my lower vantage point, I could easily determine that the noise wasn't from the large fan in the power supply, as I'd feared, but originated in a smaller (60 x 60 x 25 mm) fan which moves air directly across the processor heat sink. (You can see this fan labelled "1" in the first picture I took documenting the Sonnet CPU upgrade.) My sound level meter happened to be on my desk above me at the time: holding the device under my desk about three feet from my computer, the sound level measured over 60 dB. That's as loud as typical spoken conversation, and louder than some washing machines and refrigerators!
I didn't fuss with the fan while I tested the Sonnet CPU upgrade, hoping that removing and re-installing it might cure the noise problem. However, TidBITS reader J.J. Tiger noticed I said the fan was blowing air out the back of the machine. He contended it should be pulling air into the machine, and cited Apple service documents backing him up. Another "Aha!" moment: my fan had been blowing the wrong way for over two years! I opened the machine and changed the direction of the airflow by reversing the fan in its plastic shroud - no rewiring needed. I hoped that would be the end of my phantom noise.
Alas, no: within a few days I had the loud hum again. I completed the Sonnet CPU upgrade review, then took a more direct approach with the fan: I peeled off (but saved!) a sticker identifying its make and model and put a small drop of mineral oil into the exposed spindle. Success! The humming went away... for a month. By that time I was less charitable (and in more of a hurry): the fan got a squirt of WD-40. Success... for a few weeks. As my frustration grew, a few Google searches revealed other QuickSilver owners who experienced perhaps-similar sounds: none of their fixes seemed to apply to my situation, so my fan kept getting squirts of WD-40, and I'd occasionally remove it and try to clean its inner workings. I also tried dampening the shroud with bits of foam and using small clamps to hold the fan more securely in the shroud - but the sound always came back. I had to face facts: it was time to replace the fan.
<http://www.xlr8yourmac.com/systems/quicksilver_ CPU_fan_mod/quicksilver_cpu_fan_ noise.html>
Full of Hot Air -- Plan A: I tried to locate new or refurbished CPU cooling fans for Power Mac G4s. The closest thing I found online was offered by We Love Macs, which advertises a fan with a white plastic shroud very different from my own. No dimensions, power requirements, or part numbers were listed for the fan itself, so I couldn't immediately determine if that would work in my Mac. But I could have missed some specs because I was aghast at the price tag: $75! Yow!
So: Plan B. I decided to play like I was a non-technical Apple customer and investigate what I felt was likely to be the worst-case scenario: replacing the part through Apple. Even though my computer is long out of warranty - and I didn't maintain AppleCare coverage on it - I called three local Apple-authorized service providers about replacing the fan. The technicians who spoke with me were uniformly knowledgeable and polite (and even returned calls promptly!) but their proposed solutions were essentially equivalent: $45 to $80 for the fan itself (they couldn't tell me for sure until I brought the machine in), plus about $45 for the minimum half-hour labor charge to install the fan. Moreover, the fan would have to be ordered from Apple, typically a 2-4 business day process which they couldn't begin until they had my machine. Although one service center said they didn't need to hold on to my machine while they were waiting for the part, the cost of replacing the part through Apple would be $90 to $125 (plus tax!), as well as potentially losing the use of my machine for at least a few days.
Cooler Heads Prevail -- Still a little aghast, I switched to Plan C. Although I'd never looked into it, I knew that folks who build and modify their own PCs often buy and upgrade cooling systems separately from power supplies and processor cards. Sure enough, I found a vast number of Web sites which cater to these do-it-yourselfers. Armed with the sticker I'd peeled off my noisy fan, I searched several online vendors for the same brand and part number used in my Mac, as well as CPU fans with the same size and power ratings.
The results were much more satisfying: prices for appropriate fans ranged from $4 to $10 each, varying by site and manufacturer, although some vendors required minimum orders of 5, 8, 10, or even 100 units. However, none of the sites I initially searched carried the exact fan Apple used in my G4.
I was confident I could use my collection of screws, clamps, and dampening material to install a new fan in the existing shroud, but I preferred to purchase the original part if possible. I'm comfortable replacing many electronic components, but I'm not an engineer and I'm not sure I can successfully select substitute components when I don't have any particular expertise with the items. (Magnetic guitar pickups, yes; cooling fans, not so much.) The last thing I needed was inappropriate wiring or power mismatch to prevent installation or cause problems further down the line - especially since I need to keep this machine running as long as possible. So I pulled my trump card and contacted Bobby Orozco, a casual acquaintance out on the Olympic Peninsula who is a marine and ham radio aficionado. (These folks are often electronics experts.) Bobby recommended contacting Allied Electronics, which has been in business since 1928 and offers a dizzying array of parts, components, and tools. And darned if I wasn't already familiar with Allied! I haven't ordered from them in years (they may not even have had a Web site, it was so long ago) but I maintain my solid-state instrument amps using components originally ordered through their catalog. And sure enough: Allied had my exact fan for $5.22. I ordered two: one to install, and one in case I goofed up.
A Breath of Fresh Air -- The fans arrived as promised from Allied with no connectors attached. This is a perfectly reasonable way to sell generic components (after all, Allied doesn't know how I'm using the fan or what connector I might need!), but it could make powering the fan via the connector on the Mac's motherboard a bit of a challenge. Fortunately, I already had appropriate crimp-on quick disconnects for some of my music equipment; they cost about $1.50 from Radio Shack. Four squeezes with needlenose pliers and I was ready to install the fan. However, users without the appropriate parts could easily splice the connector from the original fan onto the leads from the new fan. Installing the new fan was a cinch: after all, I'd already removed the old one half a dozen times for cleaning and lubrication.
I'm happy to report the results are worth every penny. The Quicksilver G4 was substantially quieter on first starting up with the new fan, and after six weeks I've yet to hear the old obnoxious vibrating hum, so this saga may finally have ended! I'd love to use my sound level meter to report how loud the machine is now, but it only measures accurately down to 50 dB: under my desk from three feet away, the Mac doesn't make enough noise to generate an accurate reading. It's still not a quiet system, but its noise level is very much improved.
The bottom line is that while keeping an aging Mac running can be a losing battle and sometimes isn't cost-effective - especially going through Apple-certified channels! - sometimes simple repairs can give these machines a new lease on life for a few dollars and a bit of electrical tape.