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Re: [RFI] Doorbell Transformer RFI ??

To: "jim@audiosystemsgroup.com" <jim@audiosystemsgroup.com>, Rfi List <rfi@contesting.com>
Subject: Re: [RFI] Doorbell Transformer RFI ??
From: JW via RFI <rfi@contesting.com>
Reply-to: JW <jwin95@yahoo.com>
Date: Tue, 15 Mar 2016 13:18:09 +0000 (UTC)
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
I've had several in the area go noisey; the mechanism would sem to involve the 
internal thermal switch cycling on and off and in the 'on' state the switch 
would seem to arc and create the 'arcing' noise often observed.

In one case the doorbell switch was shorted causing doorbell transformer to 
overheat and the thermal switch to begin to cycle. Powering that circuit off 
for half an hour or so and the xfnr would remain quiet for awhile after being 
energized until it self-heated again.

BTW, I saw these xformers in my housing addition fail mostly going from cool 
spring into the first warm month of summer.

I have no experience with the SMPS types (if they indeed exist).

73, Jim WB5WPA
      From: Jim Brown <jim@audiosystemsgroup.com>
 To: Rfi List <rfi@contesting.com> 
 Sent: Monday, March 14, 2016 10:55 PM
 Subject: [RFI] Doorbell Transformer RFI ??
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 

73, Jim K9YC

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