Epson 20 - Manual (Page 163)

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 11 and Enter.
When you choose this option, all checks for the color 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.
Floppy Disk Drives and Controller Check
Use this option to test the performance of the floppy disk (diskette)
drive(s) installed in your computer. This test includes several checks
that allow you to identify particular problems related to your diskette
drives.
Before running these tests, format a diskette to use for the tests that
write data on the disk in the drive. To test a 1.2MB drive, you can
use a 1.2MB or a 360KB diskette. However, to test the full capacity of
the drive, use only a 1.2MB diskette. In a 360KB drive, you can only
use a 360KB diskette.
Likewise, to test a 1.44MB drive, you can use either a 1.44MB
diskette or a 720KB diskette; but it is better to use the higher capacity
diskette. In a 720KB drive, you can use only a 720KB diskette.
You can select the individual tests from the following menu.
Performing
System Diagnostics C-19