Nokia RX-44 Service Manual page 103

RX-44
BB Troubleshooting and Manual Tuning Guide
Image on the display not correct
Backlight dim or not working at all
Visual defects (pixel)
Bright sub-pixels
Dark sub-pixels
Combined sub-pixel
Temporal sub-pixels
Item
1
2
Issue 1
Defect counts
Combined sub-
pixel defect
COMPANY CONFIDENTIAL
Copyright © 2007 Nokia. All rights reserved.
Image on the display can be corrupted or a part of
the image can be missing. If a part of the image is
missing, change the display module. If the image is
otherwise corrupted, follow the appropriate
troubleshooting diagram.
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), the backlight is faulty.
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 following table.
Table 8 Pixel defects
(sometimes called on-pixels or stuck-on) are
characterized by the appearance of bright/colored
pixels in, for example, black full screen picture.
(sometimes called off-pixels, stuck-off, or black
pixels) are characterized by the appearance of dark
pixels in white, red, green, or blue full-screen
picture.
defects are characterized by at least two sub-pixels
defects (bright or dim) being closer than 5 mm to
each other.
(sometimes called blinking defects) exhibit
temporal variations not related to any steady-state
video input. Temporal sub-pixel defects may be
intermittent, exhibit a sudden change of state, or
be flickering.
Table 9 Defects table
Bright dot (sub-
pixel) defect
2
Not allowed
Dark dot (sub-
pixel) defect
0
Total
2
Page 4 –33