Why do some arcade monitors need isolating transformers?
The reason for this is mainly historical. When the first video games came out, they used modified TVs. “Computer Space” (the first) actually used a real TV with Valves (vacuum tubes!). Then some manufacturers started to produce monitors which were basically TVs with the RF and IF stages taken out. The problem was, old TVs all had “live” chassis, in which the metal frame was connected to one side of the mains supply, and insulated from the outside world by the casing. This simplified the design of the power supply (sometimes it was just a big resistor which got very hot!). This was fine as long as nothing was ever plugged into the TV (except the aerial (antenna) which could easily be isolated using a capacitor). But when games came out, there was a need to connect a game board, and also safety issues which meant the chassis had to be no longer connected to mains, but to safety ground, hence the need for a transformer. No currently produced monitors use these. If your monitor has a trans
