You may need to replace the power lead as it's probable that the earth wire at one end or the other has become disconnected and these leads are usually non-repairable due to the moulded connectors fitted to them. Also, the lead could have been damaged by heat generated when lightning went to earth and the insulation may be weak or almost non-existent so it's probably best to replace even if it checks out OK.
HTH
    BarryKeith

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