Samsung PS42B451B2WXXU Service Manual page 45

Troubleshooting
② Abnormal Display(Abnormal Image is on Screen.(except abnormality in Sustain or Address))
▶ Abnormal Display is related with Y-MAIN, X-MAIN, Logic Main and so on.
This page shows you how to check the boards, and the following pages show you how to find the defective board.
Samsung Electronics 4-13