Epson 10020 - Manual (Page 170)

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 then
Enter to display the error message.
Video Check
To check the video output of your monochrome adapter, press
4 followed by Enter. This check displays two different screens,
black and intensified white. First you see the black screen; press
any key to display the intensified white screen. Then press any
key to end this check.
You can use this display to adjust the size of the display on the
screen. The vertical and horizontal adjustments are located on
your monitor.
Sync Check
This test is provided for service purposes only. If you
accidentally select this option, press any key to end the test.
Run All Above Checks
To run all the tests on the menu in sequence, press 6 and
Enter. When you choose this option, all checks for the
monochrome adapter and CRT are performed automatically in
sequential order. Although you do not start each test, you must
still supply the appropriate responses to progress from one test
to the next.
Performing System Diagnostics D-13