Better results may be obtained by lifting the ground from the male end of the power cord. This assumes you feel confident in tackling the job, and your cables are not the molded factory variety.
I have seen many pieces of electronics fitted with the familiar IEC chassis connector employing a three pin power cable. Upon opening the chassis, only to find that ground pin was never connected.
In other words, it only appears to be grounded, when the manufacturer never intended it to be. This is not all that unusual, as I have seen this at least a half dozen times.