Bally/Midway Sound wiring

Mongo

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On the Bally power supply schematics for games like Galaga they have some lines labeled as +12 return. These lines are always associated with the sound circuitry. I typically see these tied to ground when a switcher is used to replace the original supply. What is the function of the "return" designation on these lines?
 
"Return" frequently means ground. Ive seen them on Bally/Midway games and earlier Atari games.
 
Yes.... but does anyone know why they use the term "return"? I know it is not a whatever to English translation issue such as when you see "ground" referred to as "earth". It seems to only be on audio circuits which leads me to believe it is an audio term that has made it onto the schematics. I just like to know these things in case I am working on a stereo or old radio and run into the term.
 
It is just "old school" for DC ground. They used to teach it that way. Positive goes to the load on this line and returns on this other line. The person writing up the scat was "old school".
 
Good to know. I was thinking that it had something to do with the load ultimately feeding a coil (speaker) that might denote that it was sensitive to inductive noise or something...
 
Yes.... but does anyone know why they use the term "return"? I know it is not a whatever to English translation issue such as when you see "ground" referred to as "earth". It seems to only be on audio circuits which leads me to believe it is an audio term that has made it onto the schematics. I just like to know these things in case I am working on a stereo or old radio and run into the term.

Because you want to separate the ground currents so the impedance of the ground lines don't cause voltage fluctuations in other circuits.

The current comes from the 12V line and returns to ground through the 12V return.
 
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