Binary Blaster Assembly Guide
QCPete 
Troubleshooting Buttons
Is one of your buttons not lighting up? Don’t fret, there is an easy way to fix it! The most common cause of a failing LED is incorrect polarity. We have designed a special trick into the Binary Blaster PCB to fix this. You can simply cut the two traces, and close two jumpers. This will swap the polarity without having to remove the button.
First, find the solder jumpers next to the button you are troubleshooting. There are two jumpers per button. They are located on the bottom side of the PCB, near each button.
Each jumper has a small trace connecting the middle pad to the default polarity setting. The small trace is sometimes difficult to see, but it is a thin stripe of metal that should show up as a lighter color red. Using a hobby knife (aka x-acto knife), cut the default traces:
Using your soldering iron, close a jumper between the middle pad and the other outside pad:
The polarity of the traces running to that LED should now be swapped, and your LED should be lighting up.