Sound board supply facts

All System 3-7 sound boards need +5, +12 and -12 V DC, made on the board from about 18 V AC from the transformer through a bridge rectifier and a regulator. There are test points for each voltage. +5 V outside 4.75-5.25 V points to the regulator or bridge. The volume pot is 5k.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• Which sound board each game uses
• Sound board jumpers for 2K sound-only games
• Using the sound board test switch
• Powering a sound board for testing
• How System 3-6 games trigger sounds
• The sound board is its own computer
• Type 1 and type 2 sound boards and their switches
• Setting up a sound board for speech

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)