Above all, the modifications made must be reversible. I do not want to inflict any permanent damage or changes to the cabinet. I will simply add lighting, make a ROM hack to control the lights, and mount an additional board inside the cabinet.
At first it didn't power on properly, and the LED driver chips got VERY hot. Then I remembered that the circuit diagram I was referring to while soldering this up was incorrect and had power and ground reversed to the chip. I also had + and - wired backwards for the LEDs as well. I forgot that these driver chips sink current, rather than sourcing it. After a little bit of emergency soldering, all of that got worked out.
I've since cleaned up the wiring a bit, adding some insulation.
I decided to wire up the LEDs such that the current limiting resistor was wired up with the LEDs, rather than on the main board. I'm glad I did this, as the resistance I picked (220 ohms) was way too high.
Enhanced image. It sadly doesn't look quite this intense in person.
Experimenting with how it will look to have LEDs inside of the joystick to illuminate it.
The output from these LEDs was much dimmer than I was hoping for. I will be experimenting with lower-valued resistors, as well as possibly doubling-up LEDs for lighting the various artwork elements. I also need to figure out how to mount the LEDs without damaging the machine at all.
Next up is the ROM hack to talk with this!
(NOTE: This article has also been published to the Interlock blog.)