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Changing the display and keyboard illumination color
You can make
your phone cool looking just by changing the color of the lights.
The green color is so common that others easily notice different
colors. The procedure is easy for an experienced electronic hobbyist.
WARNING! Although the author
succeeded in the operation described below, no guarantee can
be given for the instructions. Opening and soldering components
in a mobile phone contains always a risk to damage the equipment
seriously. Electrostatic discharge can damage the device without
any visible handling mistake.
Introduction
The illumination of a Nokia 5110 / Nokia
6110 phone is implemented with 12 SMD (surface-mount) LEDs. The
LEDs are connected in to six-LED groups: six LEDs are directly
connected in parallel with a simple current-sink. Both groups
have their own current-sink. The keyboard LEDs are driven with
slightly higher current than the backlight LEDs.
The LEDs must be driven with a constant-current sink because
the power is taken directly from the battery supply line VB.
The VB voltage varies between 3.0 V and 5.1 V! The
current flow through one group seem to be approximately 40 mA
(6.7 mA / LED).
The display group consist of special LEDs with horizontal
light direction (the LEDs light the plastic display backlight
diffuser from the sides). These LEDs may be replaced with standard
0805-size LEDs, if they are soldered on their sides. Even size
1206 works, but it requires more careful soldering (there is
not too much space for the display element).
The keyboard LEDs are of size between 0603 and 0805. They
are soldered normally. Even size 1206 can be used, but it is
quite hard to solder because these big LEDs covers the footprints
entirely and heating them is impossible.
Step-by-step
instructions for Nokia 6110
The both groups of LEDs must contain same
type of LEDs because they share a common series resistor. If
you try to use different LEDs in a single group, some LEDs may
light dimly or not at all. Refer to table 1 for LED parameters.
Table 1. Possible LED types for Nokia 6110
style phones.
|
Group |
Size |
VF |
Soldering |
|
Display LEDs |
0805 (1206 possible) |
preferably less than 2.5 V |
on the side |
|
Keyboard LEDs |
0603 (0805 possible) |
preferably less than 2.5 V |
normal mounting |
Red color is easiest to obtain
and is enough different than the normal green. Also blue and
white colors would be interesting but much harder to obtain.
One source for 0805 red LEDs is the RS-catalog,
article number 429-552 (five LEDs per package).
 Helsingissä
RS-luettelon LEDejä voi tilata mm. Yleiselektroniikka
Oy:n myymälässä. Toimitettaessa normaalitoimitusten
mukana Suomeen ja myymälästä noudettaessa ei toimituskulujakaan
tule. Hinta vuonna 1999 oli 28,65 mk pussia kohden (RS-luettelon
tuotenumero 429-552, viisi punaista 0805-LEDiä) (sis. ALV).
HUOMAUTUS! Tilaukset ja tuotteiden haku pitää
tehdä Yleiselektroniikan Teollisuuskadun myymälästä.
Puhelimitse ja postitse LEDejä ei saa. |
Before starting check that you have a Torx T6 screwdriver,
a soldering iron with a sharp tip, desoldering braid and thin
solder wire (for SMD soldering). And of course enough soldering
skills and good luck.
Preparing steps
1. Open the phone by removing the battery and unscrewing
the four screws on the back.
2. After unscrewing hold the phone face
down all the time and lift the bottom end of the phone from the
face cover. The upper end of the cover is locked with two
clips near the IR panel. To remove the cover you have to slightly
lift, and push the phone to the IR-port direction. Do not try
to remove the cover completely without first checking the way
to open the clips - it is hard to explain so check it by yourself.
Note: Hold the face plate
cover of the phone face down all the time. The earphone
will be freed when removing the cover and will be then safely
carried by the face cover. Do not touch the display lens inside
the cover or the display itself on the phone. The fingerprints
are rather hard to clean.
3. Put the cover plate in
a safe place face down and continue with the phone. Now you
can turn the phone face up. You will see the keyboard six LEDs
between the keyboard contacts. Do not touch the components or
the copper contacts on the circuit board if not necessary.
4. Open the two screws above
the display module and then lift the top circuit board from the
phone. There is a conducting wall element between the boards
- if it is stuck on the board you are removing, push it firmly
down back onto the bottom board. The microphone is mounted on
the reverse side in the bottom part of the board, do not try
to remove it.
Changing the
keyboard LEDs
5. Check the polarity of
the keyboard LEDs. It can be done for example with DMM diode
range (must measure forward voltages up to 2 volts). The COM
probe is at the cathode when there is some measurable voltage
drop; wrong direction is shown as infinite in the multimeter.
Other possibility for testing is shown in figure on the right.
The - probe is at cathode if the LEDs light. Remember to check
all six keyboard LEDs. One possible LED arrangement is shown
in picture on the left. Please note that it may be possible that
all Nokia 5110/6110 series phones are not similar!
6. With the normal ESD precautions,
desolder the keyboard LEDs. Avoid touching the keyboard contacts,
especially solder on them will cause problems. If you are not
going to reuse the LEDs, you can try to heat both ends of the
LED simultaneously by carefully pushing the side of the LED with
the soldering iron tip side.
7. After removing the LEDs, clean the footprints with desoldering
braid. Solder the new LEDs carefully onto the pads. It is
better to check the LED polarity twice before soldering.
8. Put the keyboard circuit board back into the phone.
Screw back the two screws in the top of the board. Do not overtighten.
While pressing the bottom part of the circuit board gently into
the phone (normally it is pushed by the face cover) install the
battery on the phone. Use a small part of paper under your finger
to avoid fingerprints on the keyboard contacts. After installing
the battery, you can use a clothespin to press the board. Avoid
releasing the pressure while the battery is installed, change
your finger to the clothespin "on-the-fly".
9. Press the metallic power button of the phone. Check
that the phone powers on normally. All new LEDs should light.
If not, immediately turn of the power and remove the battery
while pressing the bottom part of the circuit board. Remove the
board and check the connections for soldering failures.
10. Measure the voltages over the two 15 ohm series resistors
marked with "150" in the bottom part of the board.
The voltage over the other (usually the right one) should be
the normal 600 mV (that is: 40 mA current trough the display
LEDs), the voltage over the other is dependent of the LEDs you
soldered. If the illumination is switched off while measuring
press the power button shortly to turn the lights back on. The
constant current sink is not ideal and the voltage may be wrong.
In that case, you must adjust the resistance of the series resistor.
11. Switch off the power and remove the
battery while pressing the bottom part of the circuit board.
Remove the keyboard circuit board and solder a new 0603 resistor
on the top of the 15-ohm series resistor. The required value
depends on the voltage you measured, so no exact value can be
given. The target is to adjust the current though the resistor
to 40 mA. The current though the two resistors connected in parallel
is calculated with equation (1). For example, if you measure
440 mV (a possible value with the RS-components 429-552 LEDs)
voltage drop in step 10, you can try to solder a 20-ohm resistor
on the top of the original 15-ohm resistor (that is 8.6 ohms
together). Repeat the steps 8...10. If the voltage is now about
340 mV, you will get 40 mA from (1) and the current is correct.
Normally you have to repeat the steps 8...11 a few times to obtain
the correct value for the new resistor. However, the current
is not critical; ±10 % accuracy for the 40 mA "sounds
good".
|
(1) |
Changing the
display LEDs
12. Remove the display module from the keyboard circuit
board by carefully pushing the four clips outwards behind the
board. Avoid touching the display surface because it is rather
hard to clean.
13. As in the step 5 measure the polarity
of the display LEDs. Note the location of the LEDs carefully
because the new LEDs must be soldered exactly in the same places
on the footprints. There is no extra space under the display
module for slanting LEDs.
14. Repeat the steps 6 and 7 for the display LEDs.
Note that you must solder normal SMD LEDs on their sides to get
them light parallel to the circuit board. The direction is naturally
to the middle of the board.
15. Paste small pieces of paper-based tape on the top of
the LEDs. This is to ensure that the metallic display module
will not touch the LED contacts. Push the circuit board carefully
back onto the display module (it is easier to push the board
into the module than in the opposite way). Try to make all four
clips to snap simultaneously to avoid misalignment in the zebra
pad. If the module will not snap into its place, there may be
some of the new LEDs soldered in wrong position. They may be
under the edge of the display metal or under the plastic diffuser
element. There are only small pits in the diffuser for the LEDs.
16. Now iterate the steps
8...11 until the current is adjusted to the original value.
If you are using same type of LEDs as in the keyboard, you can
use the same resistor value without any iteration. Check especially
that the display shows the texts correctly. If not, try to reinstall
the display module and check that there is no new LEDs pushing
the module to any direction. This may require resoldering some
LEDs.
Assembling the
phone
17. Remove the battery if you have not removed it after
the current measurements. Hold the phone cover face down
and push the top of the phone into the clips of the cover. After
ensuring correct installation of the top part of the cover, push
the bottom end of the phone onto the cover and screw the four
screws back that were removed in step 1. Remember to hold the
phone and cover plate face down until the screws are tightened.
Do not overtighten.
©
Copyright 2000, 2002 Panu Tuominen. All rights reserved. Republishing
this document partially or completely is forbidden. Internet
hyperlinks to this page are allowed and such linking is encouraged.
You are doing everything at your own risk. See the WARNING! in
the top of this page.
25.1.2002 nuukiaworld@gmail.com
Email replies not guaranteed.
