Oki 390/391 Handbook page 47

To run the Font Test:
1. Be sure paper is loaded.
2. Turn off printer.
3. Hold LF button for several seconds while turning printer on. (IF printer simply
turns on without starting to print, you didn't hold down LF button long enough.)
Rolling ASCII Test
The Rolling ASCII Test produces a continuous printout of all ASCII characters. The
printing will continue until you stop it manually by pressing the SEL button. Here's a
sample portion of a Rolling ASCII Test:
40 Operation