IBM 6150 Hardware Maintenance Manual page 222

TNL SN20-9843 (03-27-87) to 75X0152 or 75X0166
Step 3
Try to set the Brightness and Contrast controls to the desired level.
Contrast Control
=~~~=~=~Q~--
Brightness Control
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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.
(3/87) Problem Isolation Charts 3-5400-3