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Re: It would appear that EVERYBODY has missed the most important item.

"So: Now you have some idea on how high end line cords can screw up a standard linear power supply."""

"More importantly, you have shown that a line cord can indeed affect the system. That is a very important point. Thank you for presenting your results."

There was never any doubt in this. I don't know why you would find this surprising. NEC recognized this a long time ago. That is why the code changed with regard to grounding conductors. It used to be common practice to run a ground wire from the neutral of a 480/120-208 transformer referred to as a derived source through an EMT or rigid conduit to building steel to physically protect it form accidental damage. But we learned especially from experience with SMPS devices that the ferrous material in the conduit created a high impedence path for harmonics during an upset condition (fault) and therefore the equipment was effectively ungrounded at those frequenies. Electricians were advised to go back and install a bonding jumper at one end of the conduit to the wire effectively making the conduit part of the conduction path. Now they are routinely run in PVC pipe except in return air plenums where they may be run as bare copper. I've often wondered whether or not or to what degree devices which surpress harmonics compromise the performance of SMPS based equipment. Clearly the best power cord is the one with no ferrous surpression at all. That is best done by a filter network, not a power cord and Dan's experience proves it. But some people will try anything and others will surely buy it on blind faith alone.

BTW, when I first saw the appearance of ferrous beads on the market offered to DIY power cord tinkerers, I wrote to UL to find out what they thought about it. They were not amused.


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