Earth pin missing

Hum loops can be an audio problem. It is similar to diverted neutral currents in PME systems, and can be very difficult to deal with under certain circumstances. However, the problem here is that the PAT testing is again not being carried out correctly. The (portable?) equipment is not each item making up the system, but the system as a whole. It has been assembled from often a very large number of items, and if these are all disconnected by an unskilled person, they are unlikely to reassemble the whole correctly and this is often very expensive to correct. Usually, such systems are assembled in metal cabinets or racks, and that is the earth reference to test, not some random radio mic (usually class 2) or similar. The whole system will have a single supply source, and that is the point to test Earth continuity, insulation etc. A single reference in the record for the whole system as being satisfactory, and a single sticker if you wish is the result. I have had to deal with this kind of mess too many times, why anyone thinks that one piece can fail and the whole system can then pass is completely beyond me, but them PAT is the lowest level electrical job available, although it should not be as the inspection is the important part, not some magic "automatic" result from a machine.


Earth continuity of such equipment may not be via the mains socket, but it is there all the same as anything else will be heard as a very loud hum immediately. The equipment does not need an isolating transformer, numerous audio transformers or to be designed as entirely balanced. Such suggestions are the result of completely inadequate knowledge of this imagined problem. A missing plastic pin just makes it impossible to plug into a BS1363 socket. It is NOT an electrical failure, and the PSU has actually failed "safe", hasn't it? Just to make it clear too, balanced systems can still have earth loop difficulties, the common-mode rejection of balanced systems is not infinite, and any hum at all above the inherent noise level should be completely unacceptable.

Hum loops can be an audio problem. It is similar to diverted neutral currents in PME systems, and can be very difficult to deal with under certain circumstances. However, the problem here is that the PAT testing is again not being carried out correctly. The (portable?) equipment is not each item making up the system, but the system as a whole. It has been assembled from often a very large number of items, and if these are all disconnected by an unskilled person, they are unlikely to reassemble the whole correctly and this is often very expensive to correct. Usually, such systems are assembled in metal cabinets or racks, and that is the earth reference to test, not some random radio mic (usually class 2) or similar. The whole system will have a single supply source, and that is the point to test Earth continuity, insulation etc. A single reference in the record for the whole system as being satisfactory, and a single sticker if you wish is the result. I have had to deal with this kind of mess too many times, why anyone thinks that one piece can fail and the whole system can then pass is completely beyond me, but them PAT is the lowest level electrical job available, although it should not be as the inspection is the important part, not some magic "automatic" result from a machine.


Earth continuity of such equipment may not be via the mains socket, but it is there all the same as anything else will be heard as a very loud hum immediately. The equipment does not need an isolating transformer, numerous audio transformers or to be designed as entirely balanced. Such suggestions are the result of completely inadequate knowledge of this imagined problem. A missing plastic pin just makes it impossible to plug into a BS1363 socket. It is NOT an electrical failure, and the PSU has actually failed "safe", hasn't it? Just to make it clear too, balanced systems can still have earth loop difficulties, the common-mode rejection of balanced systems is not infinite, and any hum at all above the inherent noise level should be completely unacceptable.