Philips BDL4785SL/00, Service Manual

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16 BDL4 7 85 S L LCD
Philips Pixel Defect Policy
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Philips' Flat Panel Displays Pixel Defect Policy
Philips strives to deliver the hi g hest qu a lity products. We use so m e o f the
industry's m ost a dv a nced ma nu fa cturin g processes a nd pr a ctice strin g ent
qu a lity control. However, pixel or sub-pixel de f ects on the PDP / TFT p a nels
used in Pl a s ma - & LCD- displ a ys a re so m eti m es un a void a ble. No
ma nu fa cturer c a n g u a r a ntee th a t a ll p a nels will be f ree f ro m pixel de f ects,
but Philips g u a r a ntees th a t a ny Pl a s ma - & LCD- displ a ys with a n
un a ccept a ble nu m ber o f de f ects will be rep a ired durin g the w a rr a nty period
in line with your loc a l g u a r a ntee conditions. This notice expl a ins the di ff erent
types o f pixel de f ects a nd de f ines the a ccept a ble de f ect level f or the
BDL4651VH LCD screen. In order to qu a li f y f or rep a ir under w a rr a nty, the
nu m ber o f pixel de f ects m ust exceed a cert a in level which is g iven in the
re f erence t a ble. I f the LCD screen is within speci f ic a tion a w a rr a nty
exch a n g e / cl a i m b a ck will be re f used. Addition a lly, bec a use so m e types or
co m bin a tions o f pixel de f ects a re m ore notice a ble th a n others, Philips sets
even hi g her qu a lity st a nd a rds f or those.
Pixels and Sub pixels
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A pixel, or picture ele m ent, is co m posed o f three sub-pixels in the pri ma ry
colors o f red, g reen a nd blue. M a ny pixels to g ether f or m a n i mag e. When a ll
sub-pixels o f a pixel a re lit, the three colored sub-pixels to g ether a ppe a r a s a
sin g le white pixel. When a ll a re d a rk, the three colored sub-pixels to g ether
a ppe a r a s a sin g le bl a ck pixel. Other co m bin a tions o f lit a nd d a rk sub-pixels
a ppe a r a s sin g le pixels o f other colors.
Types of Pixel D Dot Definition
Pixel a nd sub-pixel de f ects a ppe a r on the screen in di ff erent w a ys. There a re
three c a te g ories o f pixel de f ects a nd sever a l types o f sub-pixel de f ects within
e a ch c a te g ory.
Dot definition = What is a defective "Dot"? : One or m ore de f ective,
a d ja cent sub-pixel a re de f ined a s one "dot". The no. o f de f ective sub-pixels
a re not relev a nt to de f ine a de f ective dot. This m e a ns th a t a de f ective dot
c a n consist o f one, two or three de f ective sub-pixels which c a n be d a rk or lit.
Bright Dot Defects
Bri g ht dot de f ects a ppe a r a s pixels or sub-pixels th a t a re a lw a ys lit or "on".
These a re the ex am ples o f bri g ht dot de f ects:
One lit red, g reen or
blue sub-pixel
Two a d ja cent lit
sub-pixels:
- Red + Blue = Purple
- Red + Green = Yellow
- Green + Blue = Cy
a n
(Li g ht Blue)
Three a d ja cent lit
sub-pixels (one white
dot)
Dark Dot Defects
Bl a ck dot de f ects a ppe a r a s pixels or sub-pixels th a t a re a lw a ys d a rk or "o ff ".
These a re the ex am ples o f bl a ck dot de f ects
One d a rk dot l Two a d ja cent d a rk
dots = 1 p a ir o f d a rk
dots
Two d a rk dots,
speci f ic a tions de f ines
the m ini m u m dist a nce
between d a rk dots
Proximity of Pixel Defects
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Bec a use pixel a nd sub-pixels de f ects o f the s am e type th a t a re ne a rby one
a nother ma y be m ore notice a ble, Philips a lso speci f ies toler a nces f or the
proxi m ity o f pixel de f ects. In the t a ble below you c a n f ind speci f ic a tions
a bout:
• Allowed am ount o f a d ja cent d a rk dots = ( a d ja cent d a rk dots =1 p a ir o f d a rk
dots)
• Mini
m u m dist a nce between d a rk dots
• Tot a l no. o f a ll de f ective dots
Pixel Defect Tolerances
In order to qu a li f y f or rep a ir due to pixel de f ects durin g the w a rr a nty period, a
PDP / TFT p a nel in a Philips Pl a s ma / LCD- displ a y m ust h a ve pixel or
sub-pixel de f ects exceedin g the toler a nces listed in the f ollowin g t a ble.
BRIGHT DOT EFFECT ACCEPTABLE LEVEL
MODEL BDL4 7 85 S L
1 lit sub pixel 10 (64 g r a y)
BLACK DOT EFFECT ACCEPTABLE LEVEL
1 d a rk sub pixel 8
TOTAL DOT DEFECTS OF ALL TYPES 9
Note: * 1 or 2 adjacent sub pixel defects = 1 dot defect
MURA
D a rk spots or p a tches ma y occ a sion a lly a ppe a r on so m e liquid cryst a l
displ a y (LCD) p a nels. This is known within the industry a s Mur a , which is a
J a p a nese ter m f or "unevenness." It is used to describe a n irre g ul a r p a ttern or
a re a in which uneven screen uni f or m ity a ppe a rs under cert a in conditions.
Mur a is a result o f the deterior a tion o f the liquid cryst a l a li g n m ent l a yer a nd is
m ost co mm only c a used by lon g -ter m oper a tion under hi g h am bient
te m per a tures. It is a n industry-wide pheno m enon a nd Mur a is not rep a ir a ble.
It is a lso not covered by our w a rr a nty ter m s.
Mur a h a s been a round since the introduction o f LCD technolo g y a nd with
screens g ettin g bi gg er a nd in oper a tion 2 4/ 7 , ma ny displ a ys a re runnin g in
low li g ht conditions. This a ll a dds to the possibility o f Mur a aff ectin g displ a ys.
HOW TO SPOT MURA
There a re ma ny sy m pto m s o f Mur a a nd a lso m ultiple c a uses. S ever a l o f
these a re listed below:
• I m purities or f orei g n p a rticles in the cryst a l ma trix
• Uneven distribution o f LCD ma trix durin g ma nu fa cturin g
• Non-uni f or m lu m in a nce distribution o f the b a ckli g ht
• P a nel a sse m bly induced stress
• Fl a ws within the LCD cells
• Ther ma l induced stress - hi g h te m per a ture oper a tion over lon g periods o f
ti m e
HOW TO AVOID MURA
Althou g h we c a n not g u a r a ntee the co m plete er a dic a tion o f Mur a every ti m e,
in g ener a l the a ppe a r a nce o f Mur a c a n be m ini m ized by these m ethods:
• Lower the b a ckli g ht bri g htness
• Use a screen s a ver
• Reduce the am bient te m per a ture a round the unit