Safety aspects of users operating with HDD external USB case

Random survey on few HDD external cases with USB connector shows that even simple data backup can be hazardous to the operator. Measurements on external cases for HDD products of different manufacturers shows that some of them have problems with power supplies. Tested external cases are in operating state and function properly, but on USB shield and aluminium case on some of them 86 V to 109 V AC is measured. Although the leakage current is rather small, this does not comply with safety regulations and could induce small electrical shock for operator.