RJT> JE> I have had a small lamp on my bed bookcase type headboard for
RJT> JE> years. The pivotable arm finally got so loose it wouldn't stay put.
RJT> JE> Picked up another one at an estate sale - that worked fine. Trouble
RJT> JE> with it turned out to be a constant hum from the voltage reducing
RJT> JE> xfrmr - even when the lamp was switched off. It used a #93
RJT> JE> automotive bulb.

RJT> JE> I finally got disgusted with it and bought a new one - halogen -
RJT> JE> which does not hum when turned off.

RJT> JE> Tore (literally - the screws that held it together were imbedded 1
RJT> JE> 1/4" deep and had a head that matched  nothing I had) the old one
RJT> JE> apart. The idiots had hard wired the input of the voltage dropping
RJT> JE> transformer directly tp the 110 V AC input. The on/off switch only
RJT> JE> switched the 12V output! No wonder it hummed when turned off or on!

RJT>I guess that makes for them being able to use a cheaper switch,  or
RJT>something...
Correct.

RJT>The transformer primary winding shouldn't draw all that much current when
RJT>there's no load on the secondary side.  If it hums,  it's because there's
RJT>probably a lamination loose in there.  Some sort of
"stuff" applied to it
RJT>should quiet it down.

It doesn't take much current to make transformer laminations to hum. No
way of doing anything to quieten it. I had to actually >tear< it apart
just to see what was what.

Jay
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