The A20 auxiliary sound board

A20 is the smaller sound board, with a YM2151 synthesiser and an MSM6295 speech chip and two 27020 or 27040 EPROMs (A1 and A2). It does the speech and takes orders from A6. The game plays without it, just silently for voice.

Systems

• Gottlieb System 3

Related tips

• Both sound board LEDs dark
• Constant hum or odd noise from the speakers
• A5, A6, A8 and A20 plug identification
• Parts on the A5 auxiliary supply
• Sound needs the A1P4 cable
• No sound, or weak sound
• Gottlieb System 3: loud screeching from the speakers: replace the sound board capacitors
• No sound after the 12 V plug went on the speaker lead

Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)