About the -5v I found this link interesting:
https://hackaday.com/2021/10/27/vintage-arcade-used-negative-voltage-to-turn-volume-up-to-11/
\o/.k.
https://hackaday.com/2021/10/27/vintage-arcade-used-negative-voltage-to-turn-volume-up-to-11/
\o/.k.