Reducing CD-ROM Noise

in the Power Macintosh Minitower

Copyright 1998 by Jerry Farm

DISCLAIMER: I cannot be held liable for damages resulting from your use or misuse of this information. The information presented here is believed to be accurate, but you use it entirely at your own risk and you are solely responsible for determining whether it is fit for your use, and for ensuring the safety of yourself and your equipment. This procedure may affect the warranty on your computer.

There have been several reports on the web of CD-ROM noise on Apple Power Macintosh computers. My G3 minitower had the same problem--when using some CDs, it sounded like a WW II bomber ready for takeoff! (just listen! 14K aiff or 41K wav) After investigating, I found that the noise was actually coming from the computer's case, which was being vibrated by the CD-ROM drive (or sometimes just by the fan or hard disk!).

The minitower has a lockable cover latch at the back of the case. When this latch is pulled out, the side cover panel cannot be opened. The handle of this latch connects to a metal bar which runs up to the front of the computer, sandwiched between the cover panel's exterior plastic shell and interior metal RF shield. When the CD-ROM is spinning, it's vibration can drive the metal bar to vibrate against the RF shield, causing an annoying humming, buzzing or rattling sound.

On my G3, I've placed material between the metal bar and the RF shield to eliminate the rattle. This has significantly reduced vibration noise in my computer, though there is still a small but tolerable amount of noise from the CD-ROM drive itself when using some CDs

Several people have reported that this method has worked for them. One reported that it also works on the 8600 minitower (thanks Jon).


How To Quiet That Rattle

Step 1 - Shut down the computer. Remove the cover panel following the directions for "Opening the Computer" (chapter 3, page 47-50) in Setting Up Your Power Macintosh, which came with your Macintosh. Take precautions against electrical shock (for your sake) and static discharge (for your computer's sake).

Step 2 - On the inside of the cover panel, at the top front corner, find the end of the lockable cover latch metal bar. Note the location of the dimple stamped into the metal RF shield.

Inside the Cover Panel


Step 3 - Fashion a strip of padding to be inserted between the metal bar and the RF shield. The pad should be long enough to extend past the dimple (say, 1/2 inch) so that when the lockable cover latch is pulled out the metal bar is still in contact with the pad, not the RF shield. Also allow some length to fold the pad over the edge of the RF shield. The pad should allow the metal bar to slide freely, so a rubber pad may not be suitable. The pad should be stiff enough to be easily inserted between the metal bar and RF shield, and should be thick enough keep the metal bar from rattling. I also recommend the pad be nonconductive to prevent a short circuit should it come loose in the case.

I used a strip of tractor-feed printer paper edge, folded twice to a four-sheet thickness then trimmed to a length of about two inches. Card stock or thin cardboard should work also.

Four-sheet-thick paper pad, long enough to extend past the dimple and to fold over the RF shield


Step 4 - Insert the pad between the metal bar and the RF shield. Make sure the pad is centered under the dimple. Check that the lockable cover latch slides in and out freely.

Paper pad inserted between metal bar and RF shield, and folded over RF shield


Step 5 - Fold part of the pad over the RF shield and securely tape in place. Use a nonconductive tape, e.g., electrical tape or cellophane tape. Do not tape over the raised metal fingers of the RF shield which make contact with the rest of the computer.

Step 6 - Replace the cover panel on the computer and enjoy quieter computing.

Updated: 27 Feb 98