According to the fault phenomena, judgment is a tube of high pressure did not add, reason should be from the high voltage circuit to check step by step forward. 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.Ez7service manual download site