Can I use Christmas lights instead of the LED lights? How can I add a custom sound when the buzzer has been hit? On the far left side of the quiz board are holes labeled 1, 2, 3. What are they used for?
How do you connect DC adapter power source?
Sorry, no, you cannot connect christmas lights, well, at least not directly to the board.
If you have two units, then you can connect the holes marked 1,2 & 3 with the second unit to play with 8. This info is printed on the board itself.
As for the adaptor, please use a regulated 9V adaptor. You will have to cut the plug and solder the wires to the wires of the battery holder. Mind the polarity.
We have the impression that you are a novice. There is no problem with that, but the modifications you ask for require experience.
I’m sorry, but supplying modifications and teaching electronics is beyond the scope of this forum. You might want to seek help, e.g. from a friend who has more experience.
Thank you!