At 12:42 AM 11/16/2009, cdb wrote: > >a The other day I noticed that a particular CD monitor's SUMPS is >incorrectly wired - Active and Natural (sic) are swapped > >Surely, I said, any RECD's that are in end user facilities (the >monitors are used in pubs and clubs), won't work properly as they will >not be measuring the return current, and what happens if the fuse >which is now in the neutral line blows, due to an earth short, this >will leave the active wire exposed to someone rather than the >supposedly lower return tied to earth. Actually, there probably isn't much of a problem here. 1) You mention a possible RCD malfunction: I say: Not Possible. A RCD measures the difference between Line and Neutral current. Doesn't matter if the lines are swapped. 2) Fuse: is intended to protect against over-current, not a short to frame fault. Yeah - if it blows, the device is left floating at line potential. So What? You still can't touch any part of it - its a line-voltage device and all portions of that device that are connected to the mains are insulated against accidental touch. Colin - I don't mean to pick on you. When you have some free time, trace out the input side of one of those power supplies. You will most likely see that there is essentially NO difference between the Neutral and Line side of that supply, except that the fuse is in the Line side. Therefore, it just doesn't matter that L & N were swapped. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist