or other tints. Can anyone explain this behavior to me? The previous owner dumped it because of the yellow tint, which started before Christmas and lasted until yesterday.
iMacs have a particular cable in the CRT area that tends to fail and take out one of the colors with it. It's a little goofy that an internal cable would fail, internal cables are one of the least likely to fail parts.
At my daughter's school where I help out the single biggest failure mode of our 250 or so iMacs is a screen tinting problem. The techs who fix them know this failure well and it's usually a particular cable. I don't know which cable it is but I could find out.
-- JimA bout of Yellow fever may be? :-)
Kidding apart, following is what I have observed in trying to repair some PC CRT monitors. This may explain some of the responses.
Whenever there was an intermittant color problem like the one you describe, it could be traced to a bad connection on the VGA connector/cable. Once or twice, I just had to straighten a bent pin in the connector. Locating a bad wire within the cable can be tricky. Some CRT monitors use small preset potentiometers to set the color balance on the CRT. If the wiper contact in a preset becomes bad, the display can become tinted. Vibration and heat can cause the contact to intermittantly get a good connection and bring things back to normal. This is probably what happens with the slapping technique. Does anybody know if the iMac's video portion uses such presets?
Pretty much all CRT monitors (VGA, Mac, NTSC are going to have various trim pots for each color. Many of them can cause significant color distortion if they malfunction thusly.
For starters I would create a color test pattern, something like an AppleWorks Draw document with large red, green and blue objects on it. You should create it on another machine so you can set the colors correctly and have a comparison. Look at the doc on the much in question. It would probably be good to include each intermediate color, red-blue (purple), blue-green and green-red. If any of these blocks are black or blend with the white background that will tell you which color is messed up and something about what is wrong. If a primary color (R, G, or B) is black then that color signal is out. If one of the intermediate color blocks is white or nearly white then the opposite color (the one that isn't in the block) has an adjustment problem.
About something in the seller's work area affecting the CRT, it is highly unlikely to cause an overall tinting. Magnetic fields typically cause shaky pictures and add horrizontal lines in the picture. Permanent magnets (like speaker magnets) can cause localized discoloration. This is however fixed automatically when the CRT is powered off & then on - as it goes through a degaussing cycle (sort of wipes the CRT off of residual magnetic effects). Some times it may take a few degaussing cycles if the affecting magnets are too strong.
If you don't hear the decaying bong (that's what degaussing sounds like, at least to me) the control circuit hasn't reset. This is typically a thermal device (thermisistor) and it takes a while to cool off. So turn it off and wait 10 minutes and try again. If it still doesn't, give it more time. Some monitors don't run a degauss cycle on soft power up, only on plug in. So if it doesn't degauss on power up try un plugging it, waiting 10 minutes then plug it in again. I ran into this on an Apple AV model that had some real bad magnetization problem.
--
Clark Martin
Redwood City, CA, USA
Macintosh / Internet Consulting
"I'm a designated driver on the Information Super Highway"
-- 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! |
Support Low End Mac <http://lowendmac.com/lists/support.html>
iMac List info: <http://lowendmac.com/imac/list.shtml> --> AOL users, remove "mailto:"; 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/>
--------------------------------------------------------------- iPod Accessories for Less at 1-800-iPOD.COM Fast Delivery, Low Price, Good Deal www.1800ipod.com ---------------------------------------------------------------
