Epson 10020 - Manual (Page 174)

40-column Character
Set
Check
To check your 40-column character set, press 4 and then
Enter. The character fonts that are included in the internal
character generator are displayed. Check the characters
displayed on your screen against this illustration:
After checking the characters, respond to the prompt:
Is the display correct (Y/N)?
If the characters displayed match the illustration, press Y and
Enter. If they do not match the illustration, press N and Enter
to display the error message.
320x200 Graphics Mode Check
To check your 320x200 graphics mode, press 5 and then
Enter. The screen displays three colored squares-light green,
brown, and red-against a cyan background. These four colors
are Color Set 0. If they are correct, press Y and then Enter.
Performing System Diagnostics D-17