Pooh Bear wrote:


I deduced that his mains supply had a high impedance and the half wave rectification
of the hair dryer was enough to add a dc component to his ac supply which caused
excessive current in the transforrmer primary that in turn resulted in a line
frequency hum.

That probably explains why the isolating trannies on my bench vibrate
like hell when I use my heat gun on half power, even tho the gun isn't
plugged into the isolated supply.


Ron(UK)


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