OK, that cap is there to cut down on the spark when the switch is closed. Found a loose wire, flipper fixed.
But now I have no speech. The music and sound effects are heard, but no speech. Sound Test runs without any speech. I have the 5 VDC, plus and minus 12 VDC and ground on the Sound Board (D-11581) connector J-3. There are two push button switches on the left side of the CPU. Pressing the upper one marked "Sound" does nothing. Pressing the lower one puts a message on the display that says "U10 PIA Failure". The machine boots and starts a game with no Credit Dot.
I know that the sound effects, speech and music travel back and forth between the CPU and the Sound Board. The U10 is a 6821, no socket.