on 4/29/02 4:32 PM, Robert Eye at [EMAIL PROTECTED] wrote: > I want to replace the fan in my Rev A iMac with a quieter one. > > Anyone know what size the iMac fan is? > > What about a source for a quieter fan? > > (The Silencer� Cooling Fan from PC Power and Cooling looks like a good option, > if the iMac fan is an 80 or 92 mm fan.) >
My suggestion is, DON'T DO IT. I tried it, it didn't work well. The problem is the cooling fan sits right below the CRT gun. The spinning magnetic field from the fan causes a nauseating wobbling effect on the screen. If you insist on replacing it, it is a standard size 92mm fan but be sure you get a brushless fan. The spinning magnetic field is much weaker on a brushless motor than a standard one. A better way to quiet your iMac is to slow down the fan. I did that several months ago and it still runs fine. Now the hard drive is the loudest component in my mac, and heat has not been a problem (the computer is on nearly 24/7). Here's a message I posted 2/13/02 with my experience: <begin message> Just to update everyone with a Rev A-D (tray loading) iMac. I've been working on quieting down that jet engine of a cooling fan. First I tried a replacement fan. That was a bad idea. I should have predicted what would happen. The fan sits right below the CRT gun. The spinning magnet in the replacement fan created an interesting wobbling effect in the screen that quickly made me sick. I guess that's why the original fan is brushless, so back went the original fan. Next I decided that if I couldn't use a replacement fan (brushless fans aren't easy to find) then I could at least slow down the original fan. After some quick number crunching I knew I'd need somewhere between 30 and 100 ohms resistance to slow things down so I bought some 1/4 watt, 33 ohm resistors. With one resistor things were still more noisy than I wanted and that 1/4 watt resistor was also hotter than I thought prudent. With 2 resistors in series (66 ohms resistance) I got a nice quiet fan but maybe a little less air flow than I would like. Because the resistance is now spread among 2 resistors the heat each resistor produces now seems acceptable. I don't want to open the computer up again so I'm going to leave things as they are for a while (it's been 3 days now) and see how things run. So far everything's been fine. My suggestion, if anyone else wants to try this, is to use one 50 ohm 1/2 watt resistor. Give or take a couple of ohms resistance. The noise difference is truly amazing. Installation is simple. The resistor and telephone butt connectors are available at radio shack for about 3 dollars. You simply open up the machine as though you were installing a RAM chip. Once open there are 2 screws that hold the fan in place. You remove those screws and cut either the red or black wire (your choice) and crimp in the resistor with the telephone butt connectors (be sure to trim the resistor leads so that there is no exposed wire). Put it back together and enjoy a much quieter iMac. I don't believe the slower fan will significantly affect the temperature of the processor. The fan sits right on top of the processor and sucks air over the processor and blows it up into the CRT cavity. The air coming out the top of my Mac is a little warmer than before, but not much. I believe that most of this heat is generated from the CRT as it's quite cool when the CRT is asleep, even with processes running (like the distributed.net client). -- The iMac List is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | - Epson Stylus Color 580 Printers - new at $69 | & CDRWs on Sale! | SPECIAL LIST PRICES - Apple iMac CDROMs from $79.99, iMac DVD CDROMs from $99.99 3 port USB Hub $14.99, 40GB Hard Drive Upgrades $119 <mailto:[EMAIL PROTECTED]> Support Low End Mac <http://lowendmac.com/lists/support.html> iMac List info: <http://lowendmac.com/imac/list.shtml> Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/imac-list%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
