Like most LEDs, they only work one way around. Standard LEDs are marked with a single flat edge and 1 shorter leg. The SMD LEDs have a recessed triangle in the corner, these are marked as red in the pictures.
Soldering SMD LEDs
The first job is to remove the existing LEDs, you have 3 ways to remove them:
1. Use two soldering irons, one on each joint and flick the LED off;
2. Use one soldering iron and a solder sucker, can be awkward because of the size;
3. Use one soldering iron and some solder wick to remove the excess.
Once the board has been purged of LEDs, clean the board up and flux the solder pads on the board and LEDs. Position one of the replacements and quickly solder each side.
The 'normal' way to solder is to touch the tip to the device and push the
solder against the tip and the device until it melts. When soldering SMDs
this isn't recommended as the heat will kill it.
It is better to melt the solder onto the tip and quickly dab the soldered tip onto the LED, this limits the heat transfer, a flux pen will help the solder flow to the LED quickly shortening the time even more.
Once they have all been done, visually check the whole thing before testing, if any of
them don't work then check the solder joint and the orientation of the LED.
Roadster Trip Computer
This one isn't to be taken lightly, it's a £140 bit of kit and it needs a fair bit of heavy deconstruction before LEDs can be added. On this project, the old LEDs aren't replaced with similar items, they are removed and different LEDs are used.
Remove from the car and take out the Torx8 screws...
The PCB will now come free from the housing, make sure you earth yourself
before handling the PCB, you don't want to kill it before you have even started.
Using a solder sucker or solder wick, remove all the solder from the red circled areas.
Unclip the ribbon cable and the 4 edge clips.
The LCD should now come away from the PCB (not as easy as it sounds).
Flip the LCD over and you will see 4 metal tabs that have been bent inwards
to hold it all together, bend these back out and take the contents out.
Here we have the case, the light guide, the PCB and the bezel.
Wrapped around the light guide is the diffuser. This opens like a book
and can be removed from the light guide.
In the centre you will see what currently lights the LCD, 10 of the tiniest LEDs
that I have ever seen, so small I didn't see them first time around.
Remove the LED strip, there is no way we can replace those.
Using a small file, make 3 holes in the white plastic LCD holder.
These holes only have to be about 5mm long, enough for a PLCC-2 LED.
Here you can see where the new LEDs will wire to.
Put all the parts correctly back into the holder, place the light guide in with the
serated edge at the top. It was originally at the bottom.
The reason is the serated edge will cause uneven lighting.
Hold an LED up to each window that you filed out and stick with glue or tape.
I have used sticky backed neoprene rubber as it stops escaping light.
Twist the anode wires together and twist the cathode wires together (+ and -).
Solder them to the correct terminals on the board.
Check they work before you reconstruct the unit.
With everything back in place you can check to make sure it all works well.
I am quite pleased with the out come considering I only used 3 LEDs.
If you look carefully you can see 2 slightly darker triangle patches under the rev bar.
This is the area between the 3 LEDs so it was to be expected.
If you added 2 at the top it will take these spots out but I am happy.