IBM 5155 Manual To Operations page 158

5
Perform the printer self-test:
1. Press and hold the Line Feed button while
you set the printer's Power switch to On.
2. When the test starts, release the Line Feed
button.
Note: The printer self-test will take
approximately 10 minutes.
3. To stop the printer self-test before it finishes,
set the printer's Power switch to Off.
8000-2 Test
January 1984