Changing doorbell transformer

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I am getting ready to change out the doorbell transformer. It is in the garage. Is there something like a "standard" circuit that is likely on to I can turn it off? How do I make sure I have it turned off before I play with it?
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On Fri, 03 Aug 2007 12:19:57 -0400, Kurt Ullman wrote:

Have someone ring the bell and start flipping circuit breakers until it stops.
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The transformer is dead. The bell ain't ringing.
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wrote:

Then get a tester similar to this:
http://www.lowes.com/lowes/lkn?action=productDetail&productId7879-1781-GVD-504AD&lpage=none
and hold it near the transformer wires. When you flip off the brakers and it goes out , you have found the correct one.
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On Fri, 03 Aug 2007 13:15:22 -0400, Kurt Ullman wrote:

ooops
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How have you determined the transformer is bad? Used a meter on the primary and secondary windings? If you have no meter, you can identify the voltage on the primary with the 'barefoot wet finger' [1] approach. Then try the breakers until there's no voltage on the primary winding of the transformer.
[1] While standing barefoot, wet a finger and touch a wire. the secondary low voltage will produce a hair-raising shock and perhaps sexual arousal. touching the high voltage primary wiring will blow snot out of your nose, wax out of your ears, and lint from your navel.
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THis is where I would throw the main breaker to the house (or flip all the circuit breakers), replace the transformer, and then spend the rest of the day reseting clocks. Maybe before reseting the clocks, figure out with circuit its on and write it down.

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Kurt Ullman wrote:

Measure the secondary voltage with an ac meter. The secondary usually is terminated at two screws on the side of the transformer. If you measure between 15 and 30 volts ac there the transformer is probably NOT bad and something else is keeping your doorbell from working.
But, if there's voltage there and you still want to kill the 120 volt circuit feeding it, then just flip breakers off until that low voltage goes away.
If you don't have a voltmeter and are not willing to invest less than ten bucks for a usable one, then just forget about the doorbell and put a door knocker on your front door.
Then, sit around and hope you get a call from the Nobel Prize Comittee.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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I will, but when I just went up on a ladder to see if there were any numbers, it was hot to the touch. I am thinking that alone is a problem. Thanks for the tips on how make sure I don't BBQ myself.

So how about if there is no low voltage. What would plan B be for making sure I have cut off power.
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Kurt,
Very good when jmagerl said to shut the main off this will insure you got it dead and take a flash light with you, and just a hint don't just buy the transformer since what I have found is that 8 out of 10 times the problem is that the button got stuck down and burned not just the trans but the chime itself and since Home Depot sells this in a pack that costs like $2 more if that why not change it all out including the button that probably started this in the first place.
-Lucas Lucas Electric, LLC
If I had six hours to chop down a tree, I'd spend the first four hours sharpening the axe. - Abe Lincoln
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Kurt,
Very good when jmagerl said to shut the main off this will insure you got it dead and take a flash light with you, and just a hint don't just buy the transformer since what I have found is that 8 out of 10 times the problem is that the button got stuck down and burned not just the trans but the chime itself and since Home Depot sells this in a pack that costs like $2 more if that why not change it all out including the button that probably started this in the first place.
-Lucas Lucas Electric, LLC
If I had six hours to chop down a tree, I'd spend the first four hours sharpening the axe. - Abe Lincoln
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Kurt,
Very good when jmagerl said to shut the main off this will insure you got it dead and take a flash light with you, and just a hint don't just buy the transformer since what I have found is that 8 out of 10 times the problem is that the button got stuck down and burned not just the trans but the chime itself and since Home Depot sells this in a pack that costs like $2 more if that why not change it all out including the button that probably started this in the first place.
-Lucas Lucas Electric, LLC
If I had six hours to chop down a tree, I'd spend the first four hours sharpening the axe. - Abe Lincoln
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Kurt Ullman wrote:

I'll try and give you the safest ways I can think of to avoid your exposing yourself to hazardous voltages.
*****
Touch the transformer body and see if it feels like it's at room temperature or if it's slightly warmer that that.
If it's not slightly warmer than room temperature, then likely there's no power getting to it or the primary winding is open; Skip to "A" below
If it's warm, then there's power being supplied to it energizing the primary. If so, hold a piece of thin steel (like a nail file) against it as see if you can feel a slight humming vibration in that metal caused by the ac magnetic field leakage from the transformer. If you can, then start flipping breakers off until the vibration goes away and you will have found the breaker for the circuit feeding the transformer. (To be certain, leave that breaker off, wait a couple of hours, and see if the warmth you felt is no longer there.)
A. There's still two ways to go:
1. Turn off the main breaker for the house and work by candlelight or a flashlight. Turning off the main breaker should certainly have cut off power feeding the transformer. Do your transformer changing thing and then turn the main breaker back on.
2. CAREFULLY open up whatever enclosure the primary winding side of the transformer's wires go into and use a non-contacting ac voltage detector:
http://tinyurl.com/3ymghb
to sense 120 volts on one of the primary leads. Then flip off breakers until that voltage goes away. Then change the transformer and flip that breaker back on.
HTH,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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Hold the nail file against what? BTW: It is very warm to the touch. Thanks for the help.

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Kurt Ullman wrote:

Just hold it very lightly gainst the flat rectangular portion of the transformer and see if you can feel a slight "buzzing" vibration caused by the alternating magnetic field. If you can, then you're in good shape to feel it stop when you switch off the correct breaker.
Just make sure it's a steel nail file and not an "emery board". <G>
You might also be able to feel similar vibration if you hold a small magnet right next to the transformer.
HTH,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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On Fri, 03 Aug 2007 16:19:26 -0400, Kurt Ullman wrote:

Grab a small magnet and hold it close to the transformer, you should feel it vibrating. If so then have someone hit each breaker until the vibration goes away.
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Meat Plow wrote:

MP, you and I may be on track to becoming what they used to call Laurel and Hardy....."Two minds without a single thought". <G>
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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On Fri, 03 Aug 2007 17:50:05 -0400, Jeff Wisnia wrote:

LOL
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Kurt,
Very good when jmagerl said to shut the main off this will insure you got it dead and take a flash light with you, and just a hint don't just buy the transformer since what I have found is that 8 out of 10 times the problem is that the button got stuck down and burned not just the trans but the chime itself and since Home Depot sells this in a pack that costs like $2 more if that why not change it all out including the button that probably started this in the first place.
-Lucas Lucas Electric, LLC
If I had six hours to chop down a tree, I'd spend the first four hours sharpening the axe. - Abe Lincoln
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The high voltage side probably is wire nutted on. Pull the wire nuts, and check for voltage with a VOM set to AC volts (high enough scale, thank you....) and have someone flip breakers. Yelll at the person when the voltage goes from 116.83333 to 0. Have him (her) leave that breaker off.
--

Christopher A. Young
You can\'t shout down a troll.
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