Here is the serve timer. When a miss happens, or the game is reset, it triggers a 555 timer which keeps its output high for 1.7 seconds. This keeps SERVE high during that time.

You can trigger a miss or a reset using the logic inputs at left.

When STOP G or RUN is high, that also keeps SERVE high. This turns off the bounce sound.

When SERVE is high, the horizontal ball counter is kept cleared. SERVE is cleared when the timer expires and PAD1 is high. This causes the horizontal ball counter to start counting again, so the ball will be visible 508 counts later (which happens one line down and 134 pixels to the right). This is just to the right of the net. (The vertical ball counter is not cleared, so the ball's vertical position could be anything.)

Next: Score/Miss Sound.