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12Feb/211

Apple PowerBook Duo 230 – Repairing the Caps Lock LED

So, I accidently removed it whilst cleaning the keyboard when this unit arrived. Fortunately, I didn't lose it, so I started pondering the best method to stick the LED back down to the plastic film. The traces on the plastic are made of a conductive compound that can supposedly be soldered? When I tried... it all just melted! Hence the hole above where the LED should be.

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Above, you'll see that I'm going to repair this in-situ as popping all the keys out once more is something I don't even dream about.

Circuit Pens

So, from Jaycar, you can buy expensive circuit pens that supposedly allow you to draw conductive lines on surfaces. I've had one in the soldering kit for a while and grabbed it to try and fix this.

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I moved the LED into position and used the circuit pen to dab the bottom leg, providing enough goo to cover onto the actual trace on the plastic film.

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Letting this dry for a day, I then got a piece of very small wire and manually joined the top leg to the other trace. It worked fine! It worked fine until I bumped the LED and then the whole thing just flipped off the board. Turns out you can't use the circuit pens to glue things in place... you need to make sure they wont move first!

Tin Foil

Second attempt was from some googlin' that I don't need to bring up. Someone wrote that tin foil works well to conduct between the traces onboard and whatever you need to connect to. This made sense, so I cut some TINY pieces and stuck them under tape so that I could draw my own circuits. It actually didn't work too bad, but the light would fade in and out depending on where you were typing on the keyboard.

Winding/Transformer Wire

Ok, the final answer is to solder wiring to the LED's legs and then either run these along the traces on the mylar or run them all the way to the circuit board underneath. The latter will cause issues for the next human/robot who opens this PowerBook, but will prove to be the best fix. I chose the former first, just to see if I could do it.

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De-soldering the crap that was on the ends of the LED's legs was a little challenging. It was actually the trace compound from the keyboard membrane and it didn't really want to melt. After a little coercion it finally cleaned off. From there, I tinned up the winding wire and soldered long lengths onto each side.

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These were then trimmed and tinned. The next part was the hardest in this whole task: place LED where it should be glued down, twist one wire into shape of trace, twist other wire. Sounds easy enough, but without the unit being stuck in place, the wires would easily just bend out of shape and head in the wrong directions. I didn't really want to glue it first, just in case this whole experiment fails!

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I also chose the stupidest place to try and place the winding wires... on a curve in the traces? Jeez... I should've made them a little longer and put them both on the vertical straight areas. Anyway... with a lot of adjusting, the wires lined up! And.....!?

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NICE! A solid keyboard Caps Lock light!

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  1. I’ve seen this type of work somewhere else :)


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