... A cardboard [!] shield.

Apparently the Odyssey 100 does not have any user-serviceable parts inside. Only one way to find out...

At this point, the battery holder for six "C" cell batteries is visible.

The Odyssey 100 had the option of being powered by either an external wall adapter or by batteries.

Also visible at this point are the potentiometers used to adjust various parameters such as right wall position, goal position, and vertical/horizontal frequency. Who needs automatic adjustments anyway?

The cardboard shield can be easily removed to reveal the back of the board.