Nokia RM-57 Service Manual page 155

RM-57/58
BB Troubleshooting and Manual Tuning Guide
Backlight dim or not working at all
Visual defects (pixel)
Item
1 Defect
counts
2 Combined
defect
counts
Note: Blinking pixels are not allowed in normal operating temperatures and light conditions.
Issue 1
Table 11 Pixel defects
White dot defect
R G
1 1
Not allowed.
Two single dot defects that are within 5 mm of each other should be interpreted
as combined dot defect.
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Backlight LED components are inside the display
module. Backlight failure can also be in the connector
or in the backlight power source in the main engine
of the phone. Backlight is also controlled
automatically by the ambient light sensor.
This means that in case the display is working (image
OK) but the backlight is not, follow the
keyboard backlight troubleshooting (Page
Pixel defects can be checked by controlling the
display with Phoenix. Use both colours, black and
white, on a full screen.
The display may have some random pixel defects that
are acceptable for this type of display. The criteria
when pixel defects are regarded as a display failure,
resulting in a replacement of the display, are
presented the table below.
B White Dot
Total
1 1
Nokia Customer Care
Display and
6–37).
Black dot Total
defect
1 1
Page 6–35