Hi.
When changing battery on this watch:
You might want to file the snapping part of the plastic slightly on the back cover of the Pacman joystick watch. This will make it snap on easier.
It is a little difficult to snap on and when you force it to snap you twist plastic.
This is the reason so many of these do not have sound. The flexing of the plastic causes the very delicate and brittle piezo speaker to crack and break.

Trying to save the last of the Pacman watches!
~John