TV Service Repair Manuals - Schematics and Diagrams When troubleshooting your TV you will need to use schematics and diagrams to find the problem. Flat panel TV Diagram of Internal Parts and Circuit Boards Note: If your TV has power issues, consider replacing the POWER SUPPLY BOARD. If your TV has Lines across the screen and the screen is not cracked, consider replacing the T-Con Board. CRT-Cathode Ray Tube - Electronic Circuits and Diagrams CRT-Cathode Ray Tube Electron Gun Assembly. The electron gun assembly consists of an indirectly heated cathode, a control grid surrounding the cathode, a focusing anode and an accelÂerating anode. The sole function of the electron gun assembly is to provide a focused electron beam which is accelerated towards the phosphor screen.