When the game is powered up there is constant noise coming from the speakers that varies with the attract mode flashing lights.
Pushing diagnostic S/W 2 on the large CPU board does nothing. It is supposed to cause sounds to be produced that continue till the game is power cycled.
The noise mentioned above ceases when in the book keeping or diagnostic modes. The diagnostic sound test produces no sound for sequence 00-05. There is a sharp clear sound for sequence 06. Then there is noise for sequence 07. It then repeats starting with sequence 00. The instruction manual says there are only 7 sequences; 00 - 06.
When the game is played the noise mentioned above is continuous, but you can hear just over the noise some non-speech sounds made when targets and switches are made. At I assume appropriate points in the play you can clearly heard astronaut speech words over the noise.
Several times when I was cycling through the diagnostic tests for some unknown reason during the lamp test the sound system spoke, in order, the game's speech words. It did it clearly without any noise.
Is it possible that the 6808 sound MPU is not running, since the diagnostic switch (S/W 2) has no effect? Yet even without it running the game does sound the speech words appropriately as the game is played. Possibly the speech MPU, prom or ram is messed up causing the noise.