Philips BDL4677XH User Manual

Also see for Signage Solutions BDL4677XH: Brochure & specs

BDL4677XH276.4. Dark Dot DefectsBlack dot defects appear as pixels or sub-pixels that are always dark or “off ”. These are the examples of black dot defects:One dark dot Two adjacent dark dots = 1 pair of dark dots Two dark dots, specifications defines theminimum distance between dark dots6.5. Proximity of Pixel DefectsBecause pixel and sub-pixels defects of the same type that are nearby one another may be more noticeable, Philips also specifies tolerances for theproximity of pixel defects. In the table below you can find specifications about:• Allowed amount of adjacent dark dots = (adjacent dark dots =1 pair of dark dots)• Minimum distance between dark dots• Total no. of all defective dots6.6. Pixel Defect TolerancesIn order to qualify for repair due to pixel defects during the warranty period, a PDP / TFT panel in a Philips Plasma / LCD- display must have pixel or sub-pixel defects exceeding the tolerances listed in the following table.BRIGHT DOT EFFECT ACCEPTABLE LEVEL1 lit sub pixel 2BLACK DOT EFFECT ACCEPTABLE LEVEL1 dark sub pixel 10TOTAL DOT DEFECTS OF ALL TYPES 12NOTE: * 1 or 2 adjacent sub pixel defects = 1 dot defect6.7. MURADark spots or patches may occasionally appear on some liquid crystal display (LCD) panels. This is known within the industry as Mura, which is a Japaneseterm for “unevenness.” It is used to describe an irregular pattern or area in which uneven screen uniformity appears under certain conditions. Mura is aresult of the deterioration of the liquid crystal alignment layer and is most commonly caused by long-term operation under high ambient temperatures. Itis an industry- wide phenomenon and Mura is not repairable. It is also not covered by our warranty terms.Mura has been around since the introduction of LCD technology and with screens getting bigger and in operation 24/7, many displays are running in lowlight conditions. This all adds to the possibility of Mura affecting displays.HOW TO SPOT MURAThere are many symptoms of Mura and also multiple causes. Several of these are listed below:• Impurities or foreign particles in the crystal matrix• Uneven distribution of LCD matrix during manufacturing• Non-uniform luminance distribution of the backlight• Panel assembly induced stress• Flaws within the LCD cells• Thermal induced stress - high temperature operation over long periods of timeHOW TO AVOID MURAAlthough we can not guarantee the complete eradication of Mura every time, in general the appearance of Mura can be minimized by these methods:• Lower the backlight brightness• Use a screen saver• Reduce the ambient temperature around the unit