IBM 6151 Maintenance And Service Manual page 327

Step 3
Try to set the Brightness and Contrast controls to the desired level.
Contrast Control
Brightness Control
;\,IZB194
WERE YOU ABLE
TO SET
THE DISPLAY TO THE DESIRED
LEVEL?
NO Record SRN 26-540-490, the go to "Step 5" on page 3-5400-5.
YES
Continue on the next page.
(6/88) Problem Isolation Charts 3-5400-3