Al­ter­na­tive pixel ther­apy

Mac Format - - APPLE TALK -

I have a stuck or dead pixel in the bot­tom-left quad­rant of my iMac’s screen. I can’t re­mem­ber when it first ap­peared, but I’ve had the iMac for nearly five years. I’ve read about var­i­ous cures, such as rub­bing the screen with a cloth or a pen­cil eraser, but that doesn’t seem to have helped, and all the soft­ware cures seem to be for Win­dows only. What else could I try? Matt Feine I’m afraid not. Th­ese cures are all snake oil. A dead pixel is caused by a fail­ure of the cir­cuitry con­trol­ling the po­lar­i­sa­tion state of the red, green and blue subpix­els. This causes all of them to per­ma­nently block the light from the back­light. A stuck pixel is the same thing, ex­cept that one or more of the subpix­els has failed in the op­po­site po­lar­i­sa­tion, so that they al­ways let the light through. Both are caused by blown tran­sis­tors. I have a stuck pixel on one of my mon­i­tors that only ap­pears when the mon­i­tor gets hot, prob­a­bly be­cause the re­sis­tance in­creases with tem­per­a­ture and pushes a slight de­fect in the cir­cuitry over some thresh­old. Some of the myths about dead pixel cures might have started be­cause the time taken to care­fully rub the screen al­lows the cir­cuit to cool down. The only ac­tual cure is to re­place the mon­i­tor.

The huge num­ber of pix­els in mod­ern dis­plays in­creases the chance of one of them fail­ing. But they are smaller and less ob­vi­ous.

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