Backlight Circuit (PC Engine LT)

The backlight circuit that generates a high voltage (400V to 2000V when floating) AC voltage that drives a fluorescent tube backlight is inside the actual front screen, not on the PC Engine LT main board.

The main board simply provides the switching regulators 6.5V current-limited output to the backlight connector.

The backlight connector is the middle of the three.

The pin 3 (245.9Mhz pulse wave) comes only when the LCD Ribbon is connected, so perhaps it is feedback to the backlight circuit, as it also appears exactly the same on the middle pin of the backlight connector even though the two pins are not the same.

To repeat that, when the LCD Ribbon is connected, this signal appears on both the LCD Ribbon pin 1, and backlight ribbon middle pin.