Hello Friend. I don't have diagrams, but I ask you, you checked the transistors and resistors that are in the tube insert
already check the components of the screen socket, transistors and voltages, when you lose the video, the voltages of the bases of the color output transistors go to zero, normally those voltages are 2.7 volts, those voltages leave from the jungle , and discard the jungle for another already tested, and the fault persists