Its the screen wobbling due to the fan i inserted, the fan i put in is a decent Akasa one which seems to be doing a decent job of cooling my eMac but the bottom left side of the screen shakes a bit.... I think this is due to the fan being near to the CRT head with no RF shield...
Putting any magnetic field in that close of proximity to a CRT is going to cause some distortion. An electric motor relies on an electrically created magnetic field to make it spin. Essentially you're putting a magnet up against your display, causing a distortion, and wiggling it, causing the distortion to flicker and shake like that.
I would find a way to shield it or remove the fan. Long-term exposure to a magnet won't be good for your display (remember those kids in high school who got a kick out of putting magnets up against the monitors in the computer labs?).
If you can't shield it successfully, try moving the field instead.. Nothing says you cant take a queue from Apple laptop designs. The "heat piping" idea would work in large on the eMac as well. You could use a dryer hose or any appropriately sized tube/vent/duct material to pull the air out of the eMac from outside the case, keeping the fan safely away from the CRT.. It also keeps that extra magnetic field farther away from you if you can sit it behind the computer instead of in the computer.. Just an idea..
You can sheild the magnet by adding another magnet. Sounds strange, but it works. You one with reversed polarity. That is how they make "shielded" speakers for next to a crt tv. Also, make sure the fan has some sort of gasket between it and the case. That will help reduce vibrations on the case. -maestro
Xplain's use of MacNews, AppleCentral and AppleExpo are not affiliated with Apple, Inc. MacTech is a registered trademark of Xplain Corporation. AppleCentral, MacNews, Xplain, "The journal of Apple technology", Apple Expo, Explain It, MacDev, MacDev-1, THINK Reference, NetProfessional, MacTech Central, MacTech Domains, MacForge, and the MacTutorMan are trademarks or service marks of Xplain Corp. Sprocket is a registered trademark of eSprocket Corp. Other trademarks and copyrights appearing in this printing or software remain the property of their respective holders.
All contents are Copyright 1984-2010 by Xplain Corporation. All rights reserved. Theme designed by Icreon.