Boot let amplifier normal work, with oscilloscope check audio signal left aisle of to, dang left channel not ring Shi, measuring to signal entered amplifier Hou level, measurement amplifier work voltage normal, Hou level zoom tube launches level output right of zoom signal, entered output following electrical Hou terminated, measurement following electrical work voltage normal, description is following electrical touch points no right of through signal, replaced following electrical Hou fault excluded.peXservice manual download site