On 9/20/2019 10:40 AM, Ralph Mowery wrote:
In article , lcgh-
says...

I have a Sylvania 75w CFL fluorescent bulb that makes a high-pitched
whine when it is on. I could understand a 60hz or even 120hz hum, but
what could possibly make a high-pitched whine? Otherwise it works
fine, and others from the same package do not make the noise.




In the old days there was a ballast in the fixture. It was just some
laminated iron with wire wrapped around it (in simple terms) The
laminations would get loose and viborate.


Newer bulbs may have an electronic circuit and that large heavy iron
core replaced by a much smaller one and the circuit changes the 60 hz AC
to a much higher frequency so less iron can be used.



Interesting to know. I remember the first time looking at the CFL
circuit diagrams that they almost looked as complex as a computer board.