MacMini: Changing LED color from Stock White

Posted by: zittware

MacMini: Changing LED color from Stock White - 09/13/06 10:36 PM

Excerpt from my MacMini Modding project for my G35 Sedan at AustinModders.com:

The stock Intel Mac Mini has a white Power LED. Because I want the mac mini to look "stock" and right at home in my G35's dash; I'm going to spell out the details on how to mod your mac mini's stock LED color.

After many google search attempts; I have not seen anyone publish a tutorial on how to change the color of the LED in your mini. I hope the Mini Modder's enjoy this how-to.

Please keep in mind that you take all responsibility for implementing the LED mod on your Mac Mini. It will void your warranty so keep this in mind BEFORE attempting this mod. Neither Zittware nor AustinModders is liable for voiding your warranty.

First you need to dissemble your mac mini to get access to the white LED.
I did this by following two tutorials:

First being the disassembly video @ Smash's world. I elected to use the putty knife method instead of the wire method. The putty knife seemed like less effort despite the risk of scratching the mini's body. I used a Warner 1/2" Flex putty knife purchased from lowes. It had the thinest profile of all putty knifes at Lowes.

Once I had the top cover off my mini; I began carefully disassembling the mini using applefritter.com's step-by-step guide.
I stopped before removing the ram or the hard drive.

You need to remove the black tray assembly containing the cdrom and HD; but do not need to remove the CPU or Ram from the motherboard.
Posted by: zittware

Re: MacMini: Changing LED color from Stock White - 09/13/06 10:39 PM

Now the real fun begins. wink
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.

0 = Vwhite + Vr.led + Vled
or
(a) Vrled = Vwhite - Vled

Kirchhoff's current law; we know that the current through our LED must be equal to the current through our new resistor RLED.
(b) Ir.led = I.led = 20mA

Using Ohm's Law we can solve for the value of RLED:
I = V/R ; solving for R
R = V/I

RLED = Vrled / Ir.led ; knowing (a) and (b) yields:

RLED = ( Vwhite - Vled ) / ( I.led )

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.
Posted by: zittware

Re: MacMini: Changing LED color from Stock White - 09/13/06 10:41 PM

5) Mac Mini's HH LED modified


Solder the new 1206 SMT LED to your new landing pads; over the existing hole.

If using a ~2.2V LED; solder your 56ohm 604 smt resistor to the cut trace.

6) Mac Mini's HH LED reinstalled


Reattach the black foam spacer over the new LED - allowing the LED to shine through the hole in the foam.

Reinstall the LED board into it's housing.
Make sure to align the LED to the hole in the black tape.

Gently manuver the LED boards wire out the original hole.

Reassemble the black tape around the modified HH LED board.

7) Reverse your disassembly; returning the mac mini back to it's assembled form. Take care to reassemble everything.

Here's the final look; complete with an Orange power LED which will match nicely with the G35's orange iluminated dash.



See my thread at AustinModders.com for more hardware hacks on this mac mini... plans include (if sucessful) a Hard Drive activity LED, a electric cd eject button, and a CDROM access LED.
Posted by: oojacoboo

Re: MacMini: Changing LED color from Stock White - 09/14/06 10:01 AM

great guide.  Not a simple walk in the park...