PSU capacitors are a frequent source of problems.
Google for the scope's manual, and replace the electrolytics with new equivalents. Rules of thumb for aluminium electrolytics and tantalum beads are to ensure the rated voltage is double the working voltage, and for aluminium electrolytics that the capacitance is doubled. If it is a switching PSU, get a capacitor rated designed for switching PSUs, e.g. Nichicon PW series.
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