Now the real fun begins. Let's mod the MacMini power LED:
Materials needed: * High End SMT (surfact mount technology) capable soldering with fine SMT tip * desoldering wick * SMT 1206 LED color of your choice * Datasheet for the LED you selected. Need forward voltage drop spec @ 20mA. * SMT 604 resistor @ 56ohms. * hobby knife with newish triangle blade. * solder * uber soldering skillz for SMT devices
1) Remove the LED board
Remove the white LED's mini circuit board by gently pulling the black hard tape apart at the rear of the assembly. I used a hobby knife to start removing the tape. Be gentle; the black tape easily rips despite being thick.
Once the tape is free; you'll have a small circuit board double sticky taped to the back of the black housing. Use that same knife to gently pry the circuit board from the tape.
Take care with the wires attaching to this board. They are fragile and will break easily.
2) Mac Mini's LED circuit board w/ "foam" light blocker
Here's a picture of the circuit board removed. The black foam is adhesive backed; which is how it attaches to the circuit board.
I beleive the purpose of this foam is to provide a spacer to secure the circuit board in the assembly... maybe to prevent "rattle". Apple certainly knows how to spec quality assemblies.
Gently remove the adhesive foam using a hobby knife. Take care to remove with the adhesive intact on the foam (not circuit board) so you can reuse it during reassembly.
3) Desoldering time
Notice the white diode labeled D1. and the plus (+) symbol.
Using an SMT tip; desolder the diode at D1 using a solder braid. Clean up the diode pads using solder braid.
Rotate the wires by to the backside of the circuit board; one at a time; to ensure you don't accidently wire the board / LED backwards. I used a solder braid to remove the solder; then resoldered on the non component (or non copper) side.
4) MacMini's HH LED prep
Using the hobby knife; scrape off enough solder mask to mount your desired color. The author used a 1206 SMT LED - Orange from Digikey - A Stanley AA1101W.
For our calcuations; we are going to assume the forward drop of the stock white LED is a typical 3.6V. Assume typical LED currents of ~20mA.
Since we are using a lower voltage LED; we need to put a current limiting resistor (RLED) into the circuit to "drop" some voltage. Using some electrical engineering - Kirchhoff's voltage law; we know that the sum of all voltage must be zero.
From our new LED's datasheet we know that VLED = 2.2V; so:
RLED = ( 3.6V - 2.2V ) / ( 20mA) = 70 ohms
The closest resistor value the author had in 604 package was 56ohms; so we will use 56ohms in the remaining steps.
NOTE: If you are going to replace the LED with a newer color like Blue, bright green, or uv... note that the forward voltage of these LEDs is closer to the original White LED. As such; you will *NOT* cut the traces below or solder in a 56ohm resistor as calcuated above. IF IN DOUBT; check your datasheet for it's typical forward drop @ 20mA.
IF your using a standard low voltage LED (red, yellow, orange) with a Vdrop ~2.2V continue. Else skip the next step cutting the trace below.
Cut the long trace on the Kathode (+) side of the LED. Make the cut wide enough to fit a 604 SMT resistor.
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