Originally Posted by hap
Entex Raise The Devil and Electronic Poker are working.

Is there anything non-standard about the speaker setup in the poker game? If so, can you make a schematic? In MESS, I'm getting messy farts instead of beeps.

Nobody likes messy farts. ewww. I traced out the audio circuit for donkey kong. Looks like pin 53 is the audio itself and pin 35 is the "decay" pin.

There's one transistor that just turns the feeper on and off (via pin 53) and the other controls the pulldown resistor on the feeper which controls its volume. There is a 0.47uf cap and 91K resistor on the base of it, which is connected to pin 35.

This is similar to how le boom does it volume decay.

Galaxian's audio works like you said- pin 40 is the audio output, and pin 41 is the oscillator control. There's a resistor/cap circuit on pin 41 so that it can be controlled.

Looks like when 41 is low, it discharges the capacitor and stops the oscillator. When high, it will oscillate at maximum frequency, and when tristated (input mode) it will slowly decrease in pitch. I was thinking of throwing it on a scope to see what happens.