>In this case, we're talking permanent, albeit mild. I'm not sure if you're talking about the darkening corner issue here, or the "burn-in" of a long-displayed image like the menu bar. As I noted before, they appear to be different things.
The former does seem to reflect a permanent and ongoing change, related either to the age or cumulative usage of the display. The latter (image persistence), as I noted, isn't something that should ever be permanent - though it can take a surprising length of time to go away (like a week). Note that image persistence affects colour TFT displays and passive displays as well as the monochrome TFTs in the 250 and 280. I've only seen or heard of the corner issue on mono TFTs (it's on the four corners of the 280 I'm typing this on). >Based on the comments in this thread, I did a little web searching for >references on TFT burn-in, etc. I think what we're seeing is a form of >what is apparently referred to as "image sticking". > >I'm not enough of an EE to understand the references, but it appears >that the phenomenon is connected to "improper balancing of the voltages >across the liquid crystal cells." (Whatever that means.) I believe I've read this is actually caused by ion transport around the display pixels, which concentrates charge and thus modifies the electric field that allows the LCD to operate. This is why a stuck image takes time to dissipate, perhaps a long time depending on conditions. This actually happens constantly when the screen is used, but usually disperses in seconds or less. >I'm also starting to wonder if a worthwhile experiment would be to run >some kind of screen saver,specifically one which keeps the corners >changing, to see if it makes a difference. It doesn't. ;) I've only tried it once, though, so I'd be pleased if someone else did the same. In my limited testing the only thing which has any effect is the length of time the display has been operating - when the computer is woken up or started up after some time spent dark, the corners work fine at first and then the darkness creeps in gradually on little cat feet. This is how it differs from image sticking - there is obviously a change occuring, but the image (of darkness) isn't itself persistent. Rather it's the gradual loss of the ability to produce any image, even the one that might otherwise become stuck there. I also keep the Trash icon in the exact bottom-right on OS 7-9 Powerbook screens, which has the effect of cycling the spot from white to black whenever I drag something to the trash (often). That corner shows the same effect to about the same degree as the other three. Note that my bottom right screen corner doesn't have a stuck black-on white 'h', but instead a black cloud that causes the icon label there to appear as "Tras". ;) >I wonder if this implies that running something like the old MacBench >graphics tests repeatedly would run all the pixels through a wide range of >applied voltages and effectively "degauss" (if you want to make the analogy) >the LCD?? Or, a screen saver. Don't think so. If it is a buildup of charge the analogy is fairly apt, but then turning the display right off for a while takes care of things. ---------- Duo/2400 List, The friendliest place on the Net! A listserv for users and fans of Mac subportables. FAQ at <http://www.themacintoshguy.com/lists/DuoListFAQ.shtml> Be sure to visit Mac2400! <http://www.sineware.com/mac2400> To unsubscribe, E-mail to: <[EMAIL PROTECTED]> To switch to the DIGEST mode, E-mail to <[EMAIL PROTECTED]> Need help from a real person? Try. <[EMAIL PROTECTED]> ---------- Dr. Bott | 10/100 Ethernet for your 2400 is finally here! MPC-100 | <http://www.drbott.com/prod/mpc100.html> RoadTools $30 PodiumPad available at Apple retail stores, $20 Traveler CoolPad at Staples. Both in white for iBooks at <http://roadtools.com> Midwest Mac Parts ][ <http://www.midwestmac.com> After-market parts for Macs. ][ 888-356-1104 ][ MacResQ Specials: LaCie SCSI CDR From $99! PowerBook 3400/200 Only $879! Norton AntiVirus 6 Only $19! We Stock PARTS! <http://www.macresq.com>
