Fault phenomenon: after startup screen, touch screen has no high voltage electrostatic reaction. SUcservice manual download site
 SUcservice manual download site
Analysis and maintenance: according to the fault phenomenon of judging the high pressure did not add the kinescope system, reason should be from the high voltage circuit to check step by step forward. Because there is no ready-made circuit diagram, according to the PCB circuit to use oscilloscope to detect Q305 collector, no waveform change, can't afford to illustrate Q305 vibration; Check forward Q311, Q310, no waveform output. The last check to integrated block LA7851 first (12) feet no waveform output. Integrated block LA7851 first (12) for foot line oscillation output, no waveform output line LA785 oscillation output circuit is damaged; But still has its field oscillation output waveform, the field vibration work. Because the line oscillation circuit without output waveform line amplification, action, high pressure and displacement output which is not normal. After welding LA785 replacement, troubleshooting .SUcservice manual download site