CRTs don’t last forever, and neither do the electronics that drive them. When you have a screen starting to go wonky, then you need a way to troubleshoot which is at fault. A great tool for that is a ...
Design for testability (DFT) works to make a circuit more testable to ensure that it was manufactured correctly. Alfred Crouch explains the purpose of DFT in his book, Design-For-Test for Digital ICs ...