Troubleshooting doorbell?

The doorbell to my rental apartment stopped working. Knowing the simple button is the most likely point of failure I pulled it off and shorted the wires. It did not ring. So I went down to the cellar and found the transformer mounted on the side of a circuit breaker panel. Using my voltmeter I tested the voltage. None to speak of. So I replaced it. Again, no measurable voltage. Could a wire be bad? This made no sense. So I called my electrician. He said that these transformers are like that. And to test it put a screwdriver across to short the terminals. See a spark and it is okay. Hmm... So I pulled it off the panel and connected some wires to it and plugged it in. No reading on the voltmeter. If I can't measure a voltage how am I going to test for what went bad in the circuit?
Don <donwiss at panix.com>.
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It is 16 volt.

Yes.
I didn't do it. When I questioned him on this he said the transformers have a thermal circuit breaker that will open, then close when it cools off.

It is getting supply voltage. 126 volts here in Brooklyn. It is a 110-120 volt transformer. It is not a multi-tap. I have it wired correctly.
Don <donwiss at panix.com>.
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Don Wiss wrote:

did you have power TO the transformer??? if not then you not ever gonna get voltage out of the transformer.......
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YES.
Don <donwiss at panix.com>.
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In alt.home.repair on Mon, 04 Aug 2003 23:26:44 -0400 Don Wiss

I don't really understand these last 3 lines, but maybe your meter is bad. Wouldn't that account for all unanswered questions?

Meirman
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quoting:

If there's no voltage at the secondary on two transformers, then I would assume that the 120v wiring somewhere upline is bad.

hmm... If this is the case, then it could be a short in the doorbell circuit that burned up the transformers. Did you happen to feel how hot the new transformer got before it stopped working? Too-hot-to-hold heating is a sure sign of overload or shorts. It heats up too much, burns up.
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On Wed, 06 Aug 2003 07:06:50 GMT, snipped-for-privacy@verizon.net (JM) wrote:

My ohmmeter showed no resistance in the circuit, measured at the transformer wires.

It did get a little warm. But only warm, not hot. My electrician said they had thermal breakers. If so, then after cooling off it should have worked again. Not be permanently dead.
Don <donwiss at panix.com>.
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In alt.home.repair on Wed, 06 Aug 2003 14:18:52 -0400 Don Wiss

That's interesting. In practice, there's nothing you could have done to cause that. (You didn't connect more than 110.)

After I wrote what follows, I had doubts as to whether the difference I go into could possibly be big enough to matter. I also don't know if you are really interested in such things, or if you only want to do your landlordial duties. But I think I vaguely recall being tricked for a while by something which showed no measurable resistance, which still worked. (It's also why it is good to measure things when they are still working, or the replacements before they are installed.):
There may well be a short in the bell, but it's also worth remembering that the bell, unless it is some new-fangled electronic gizmo, almost certainly contains a coil or 2, and a coil presents more resistance to AC voltage than it does to the DC voltage of your meter. The higher the frequency the higher the resistance (Impedance). 60 cps is pretty low, but it will still make some slight difference. Somewhere I have a book with the formula, but it would require knowing the inductance (in Henrys) of the bell, and we don't have any direct way to measure that.
Also the secondary coil of the transformer will present slightly higher resistance to the AC voltage than it does to your meter.

Meirman
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Well, it is 126 volts here. But I did attach the new one to the shorted circuit for a short while. The old one was attached to the shorted circuit a long time. When first tested the old one had no voltage. Now it does. So it having a thermal breaker makes sense. But shouldn't the new Heath/Zenith one also have a thermal breaker? And not just a breaker that opens and then ruins the transformer?

Just a basic bell.

I spent a couple hours investigating. I removed the bell. (I did not test it.) The circuit at the wires there was open. The circuit at the transformer wires was still shorted. I checked the button. The wires were not shorted. Pushing the button and the circuit closed. I followed the wire from the transformer. It had several splices along the way. They it went above a hot air duct and then up into the sheet rock, but not below where the bell is (about six feet away). Above the hot air duct were bare wires. But I could not reach in to get to them. Not enough clearance.
I hooked up a tone generator at the bell wires. (Remember the circuit was open there.) I got a signal all along the wire in the cellar up to the transformer. I got a signal out at the button. But I could not find how the wire from the button joined the rest of the circuit. It goes into the brownstone and disappears.
It looks like I'm going to have to wire an entire new circuit. I have a choice of the electrician or the alarm system fellow. The electrician will do a top notch job of snaking the wires in the walls. The alarm guy only surface mounts. So I left a message for the electrician
He called before I could post this. He recommends buying a wireless doorbell from Radio Shack. Right now he is busy wiring air conditioners, and all the rain here in Brooklyn has backed up his work. But he may have a chance to stop by between jobs, or when he gets a last minute cancellation.
Don <donwiss at panix.com>.
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Hi Don!
DW> The doorbell to my rental apartment stopped working. Knowing the simple DW> button is the most likely point of failure I pulled it off and shorted the DW> wires. It did not ring. So I went down to the cellar and found the DW> transformer mounted on the side of a circuit breaker panel. Using my DW> voltmeter I tested the voltage. None to speak of. So I replaced it. Again, DW> no measurable voltage. Could a wire be bad? This made no sense. So I called DW> my electrician. He said that these transformers are like that. And to test DW> it put a screwdriver across to short the terminals. See a spark and it is DW> okay. Hmm... So I pulled it off the panel and connected some wires to it DW> and plugged it in. No reading on the voltmeter. If I can't measure a DW> voltage how am I going to test for what went bad in the circuit?
Good troubleshooting techniques. Wire (or connection) could be bad. Have you checked the doorbell itself? Could be the site of the broken connection, or could be a gummed up selenoid if mechanical chime type.
You probably will not get any voltage across the doorbell terminals either as the doorbell switch is open. Could remove from wall and move to site where transformer is and use test leads to check.
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Don,
It is very, very common when a transformer goes bad and the wiring between it and the bell/switch is suspect, to wire in another transformer somewhere (virtually anywhere!) and re-use anywhere from a little, to none of the existing wiring (typically I have found the "extra" transformers in attics or HVAC closets).
It may be that the transformer secondary was feeding a short circuited wire run and if this were the case your replacement, of course, wound up doing the same thing. Whether or not this happens to be the case, it would seem from a labor standpoint, running new wiring and going from there (i.e. testing or replacing the bell) would be the way to go.
Sorry so with so little, but didn't read until today...
Best,
Stephen Kurzban
Don Wiss wrote:

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