Noise from audio amp may be due to a bad filter cap. I had an asteroids arcade with a 60Hz harmonic (forget which multiple)...I used a tone generator on my phone to match frequency and deduced that it must be the ac line filter based on frequency (big filter capacitor by itself)...In this case it was more of a hum noise. If it's strictly random noise you may have a cold solder joint or some other bad connection.

Game should boot without -12 I believe--what are the status lights showing on the mpu? Did you check voltages there, too?