[RFI] Doorbell Transformer RFI ??

[Jim Brown]

I've heard for years that doorbell transformers could be noisy, yet the 
mechanism was not clear and I've never found one that was noisy.

But it just hit me -- electrical supply houses sell no-name, unlabeled 
switch-mode power supplies to provide low voltage DC for low voltage 
lighting circuits, and they CALL them "electronic transformers." Is it 
possible that the noisy doorbell transformers I've heard about are 
really an SMPS? Or is it a real transformer whose windings have 
deteriorated?

73, Jim K9YC