If you ever tried to take apart optimus' chest, you will realize it is impossible without tearing one arm, sentinel style, in order to get to a single screw behind it
, so i looked for a way to do it. In order to take apart the arm, you have to remove the pin securing it, to do it, remove the batteries and the connector. DON'T try to pull, it is EMBEDDED in the plastic, you will have to drill your way around itOnce you remove it, keep on drilling until you see the pin:
I don't know if it will be stubborn on other figures, but mine was specially hard to remove, so i took an extreme measurement: Freeze it! yep, that will make it slightly easy, for metal and plastic shrink at a different rate when cold.
You will have to work as fast as possible, to avoid defreezing the pin. With the help of a really thin screwdriver and a firm and supporting area with a hole in the middle (in my case a plastic tube) to allow the pin to be displaced, hammer it SOFTLY until the arm is free.
What you will find inside is not much, just the chest flexing mechanism, the speaker and a tiny circuit board which is basically an integrated circuit and a few resistors. The ones we are interested in are R2, R3 and R4, for they regulate the current feeding the leds.
Taking a multimeter, they read 47 ohms each. Depending on the leds you get, maybe you will have to add some other resistances in serial connection. I recommend using one line to feed the eyes and spark chamber, other for left headlights and left chest, and the remining for the right headlights and chest. In my case, it turned out that the white leds were some huge power hogs, dimming severely the other leds, so i limited the current throwing an extra resistance with 35 ohms on each line.
When puting together the headlight sets (two parallel 3mm leds per line), even when you buy the leds on the same store, some of them will not be the same, so i recommend trying them together on pairs before soldering, for the one more power hungry will devour all the current, leaving the other one very dim, so try different ones until you find a pair that looks even. Since everything was outside, i changed the green and red leds for blue ones. In order to create the spark chamber, drill a hole in the neck piece through behind just below the screw keeping everything together, carve all the front and shape it, put the led, connect it with the eye line, and mold the spark chamber with epoxy.
To connect everything, you will need the thinest cable you can find, for the chest mechanism takes almost all of the available space. Hard disk IDE data cables will do really fine.
Once you have tested that no led is dimmer than others, drill two holes below the speaker to allow the headlights to come out
Check that there is no cable interfering with the mechanism, and put the screws back. glue the headlights in place, and cut the false ones form the moving parts
Enjoy!
There will be almost no difference in places.
Excellent job. Those are tiny spots and places.
