I see what looks VERY like a D underneath the component, the silk screen mask can tell you lot. Tell him to get a better picture, or lean in there with an eye loupe and a bright light to find out what it is. For any 'back shed' experimenter I can't recommend the use of magnification more. A 10X eye loupe can actually be simply placed in front of common digital camera or cell phone to adjust it's focus to the centimeter range.
To determine how this device actually functions will require a lot more detailed photo's of both sides of the board, and an explanation of what the ribbon cable that's fed into it is attached to.
I have several photos of both sides. I'm in the process of working out the circuit diagram.
Regardless, this will not be a simple modification, and definitely not something good for someone that doesn't have good descriptions of the circuit to tell someone that doesn't know what they're doing to do
Yes, I know, but I'm prepared to persevere with him