5102P The beam of the first channel disappeared - Electronic Engineer Discuss

5102P 2017.The next time the beam of channel 1 disappeared. When you try to return it tothe center of the screen by rotating the volt / dv or vtrtical position knobs,the beam appears for a moment and immediately flies up, as if it had a highvoltage. When you press the button, MEASURE shows a voltage from 25 volts to600 volts when as always but in different ways. The sensitivity of the channelin this case is either 10 or 100 volts. Software update does not help. Andanother thing: when the sweep is reduced to the very minimum (2ns), the channel1 beam appears on the screen in the form of a regular sinusoid with a frequencyof 125 MHz. ???????