Major differences between Block I and Block II PGNCS included replacing electromechanical resolvers with an all electronic design and replacing the Block I Navbase with a frame built out of aluminum tubing filled with polyurethane foam .
The Block I Navbase was machined from beryllium .
Major differences between Block I and Block II PGNCS included replacing electromechanical resolvers with an all electronic design and replacing the Block I Navbase , which was machined from beryllium , with a frame built out of aluminum tubing filled with polyurethane foam .