I can't see the characters on my screen or the screen is all black.

If your system is equipped with a black selector knob, rotate it when powering the system on.

To adjust the screen contrast, simply turn the black selector knob while the system is powering on. You can rotate the knob to the right or left until you achieve your preferred contrast level.

Please note that if your system features a touch screen, the contrast adjustment option is not available.