Need Help: Mechanical Chime Won't Ring After Transformer Replaced

[ftresi]

Hi. Here's some background info. I am located in the United States, and have had a Nest Hello video doorbell working perfectly for a couple of years. It's powered by a 16V 10va transformer. I also have a mechanical door chime that rings when someone presses the button on the Nest Hello.

The doorbell lost power a couple of months ago. The transformer had blown. The transformer was replaced, the doorbell was good for three days, and then transformer #2 blew as well. I suspected the Nest Hello might be shorting the circuit because of stuff I had read online from others that had a similar issue. So I replaced the transformer a third time, but also removed the Nest Hello and replaced it with a simple pushbutton, and I also removed the white disc shaped capacitor that the Nest Hello comes with that's wired into the chime. Transformer #3 died after a day.

Fast forward. Turns out the doorbell wiring in the attic somehow developed a short. So that section of wiring was replaced and my 4th transformer is working (so far) without blowing. The Nest Hello now works again. BUT. It no longer rings the mechnical chime. I checked the Nest App and the Indoor Chime setting is turned on. When the bell is rung, I can see the plunger in the chime moving but not quite enough to strike the metal plate that makes the ding-dong sound.

My current transformer is a 16V 10va like the original one that worked but it's clearly not putting out a full 16V.

Could the new transformer be bad / weak and a new one might work properly? Or could the splice in the doorbell wiring be adding just enough resistance that the chime no longer gets enough power to produce an audible ring?

Now I know the thing to do is measure the voltage put out by the transformer (with and without load) and also the power at the chime. This leads to my next question. I have this multimeter (https://www.amazon.com/Cen-Tech-Dig...ocphy=1022987&hvtargid=pla-591185389125&psc=1) but am not quite sure which settings I need to use to measure the power put out by the transformer.

Can someone please advise how to use my model multimeter and also whether a different transformer would work properly?

Thanks!

 

[marconi]

Greetings from London.

Could you disconnect briefly the wires to the NEST door bell at its terminals and then touch these wires together - does the door chime now ring? Do this test a few times.

Now reconnect the NEST door bell. Ask someone to press the NEST door pushbutton while you measure the voltage at the terminals of the chime. The voltmeter needs to be on the AVC 200 setting (the knob a few minutes after 12 o'clock). Then do the same test at the output of the transformer and then the terminals of the doorbell. Please tell me these pairs of voltages.

Does the NEST door bell work in all other respects? eg the video?

Last please post me a picture of the disc shaped capacitor which includes any markings on it.

Which NEST door bell do you have?

Have you replaced the transformer with one exactly the same as the one one when all worked fine?

Because it adds to my interest - where are you in the USA please?

 

[ftresi]

Greetings from London.

Could you disconnect briefly the wires to the NEST door bell at its terminals and then touch these wires together - does the door chime now ring? Do this test a few times.

Now reconnect the NEST door bell. Ask someone to press the NEST door pushbutton while you measure the voltage at the terminals of the chime. The voltmeter needs to be on the AVC 200 setting (the knob a few minutes after 12 o'clock). Then do the same test at the output of the transformer and then the terminals of the doorbell. Please tell me these pairs of voltages.

Does the NEST door bell work in all other respects? eg the video?

Last please post me a picture of the disc shaped capacitor which includes any markings on it.

Which NEST door bell do you have?

Have you replaced the transformer with one exactly the same as the one one when all worked fine?

Because it adds to my interest - where are you in the USA please?

Thanks for replying,

Before I connected the Nest doorbell, I tried touching the two doorbell wires together and it did ring the chime. It was only after connecting the Nest that the chime stopped working. I did that initial test just to make sure the transformer worked before connecting any doorbell button.

The doorbell works in all other respects. The video is fine and it seems to work as it should.
I have this model - Nest Hello Doorbell - https://store.google.com/us/config/nest_hello_doorbell?gclid=CjwKCAiA_eb-BRB2EiwAGBnXXkbErNIlPtJjYBRJXz-ryS7-7r5vwMoEWjLz8HoyOoaDk3M-Ps97exoC2WkQAvD_BwE&gclsrc=aw.ds

The current transformer has identical specs as the last one that worked fine. The difference is that the original one was probably 20 to 30 years old and made in the USA and the new one is made in China and probably not nearly the same quality as what I had originally.

Thanks for the tip on using my multi meter. When I have some time, and someone else at home to help me, I'll check all the voltages and post them, along with the picture you requested.

And finally, I am in New York.

Thanks again for your help. It's appreciated.

 

[DPG]

I'm intrigued by the removal of the capacitor (if it is indeed a capacitor)

 

[marconi]

Thank you for the information which I will ponder on. I cannot respond any more tonight. I will be back in touch once you have reported those voltages and posted a picture of the capacitor.

 

[ftresi]

I'm intrigued by the removal of the capacitor (if it is indeed a capacitor)

I can remove it and see what happens. It's officially called a Chime Connector. Here's some info I found on what exactly it is.

https://www.reddit.com/r/Nest/comments/bmcf0p

 

[marconi]

Was the short circuit at the red link or the purple link - see my scribbled attachment? Or in other words in which position did you do the repair to the wiring?

 

[ftresi]

Was the short circuit at the red link or the purple link - see my scribbled attachment? Or in other words in which position did you do the repair to the wiring?

The red link was repaired - the wiring starting at the transformer and going to the chime. The wiring from the door to the chime seems OK and was not touched.

 

[marconi]

The disc must be used (even if you don't use a chime). It must be connected as in my attached diagram.

 

[marconi]

In my post #7 I attached a diagram which had the long run to the door chime C and asked you where the short circuit was. There is another wiring scheme which you may have though in which the long run is to the Nest Hello door push N; I have sketched this out and attached it.

Please would you study the two diagrams in #7 and here in #10; which is closest to your installation in terms of where the 'long run' heads to?

If your installation is more like the diagram here in #10 where was the the short circuit/repair done - at green or yellow? If it was more like #10 then you can see there is the possibility of causing damage to the transformer and the disc if the short was at the yellow point whereas only damage to the transformer at the green point.

 

[ftresi]

In my post #7 I attached a diagram which had the long run to the door chime C and asked you where the short circuit was. There is another wiring scheme which you may have though in which the long run is to the Nest Hello door push N; I have sketched this out and attached it.

Please would you study the two diagrams in #7 and here in #10; which is closest to your installation in terms of where the 'long run' heads to?

If your installation is more like the diagram here in #10 where was the the short circuit/repair done - at green or yellow? If it was more like #10 then you can see there is the possibility of causing damage to the transformer and the disc if the short was at the yellow point whereas only damage to the transformer at the green point.

The run that was repaired is at the green point. The wiring from the chime back to the door (yellow) didn't have to be repaired.

I need to do some homework and take voltage readings. I will also try removing the chime connector to see what happens. And maybe try reversing the wires (could reversed connections to the chime cause this problem???).

I'm busy this week with assorted things but am taking about two weeks of time off from work starting next week so I'll have time experiment then.

Thanks again.

 

[marconi]

The literature for the NEST Hello says it should not be used without the Chime Connector in circuit. The orientation which matters is to do with the Chime Connector wires: when the NEST Hello and Chime Connector was first unboxed the wires which were into connectors are connected on the Nest and Transformer side. The wires without connectors go to the chime if used or are each insulated.

 

[ftresi]

The literature for the NEST Hello says it should not be used without the Chime Connector in circuit. The orientation which matters is to do with the Chime Connector wires: when the NEST Hello and Chime Connector was first unboxed the wires which were into connectors are connected on the Nest and Transformer side. The wires without connectors go to the chime if used or are each insulated.

Correct - that's how the chime connector is connected. I was just wondering if maybe the two ends without connectors (that screw onto the chime terminals) are reversed. Could that cause my problem? Could I cause any damage by trying to reverse them?

 

[marconi]

Yes try reversing the connections to the chime as you suggest but at the moment I do not think that is the problem since we are dealing with alternating current. But I may be wrong and the chime connector outputs direct current and your chime may be sensitive to the polarity of the applied current.

 

[ftresi]

I finally had some time to look at this some more. I am happy to report that all is working now.

I took a closer look at the chime and it works now. I think what probably happened is that one of the wires was interfering with the spring on one of the plungers and it was keeping it from striking the plate. I stumbled upon this accidentally when I poking around inside there and suddenly all worked.

So I feel a little dumb but am happy that it turned out to be a very simple problem. I'm not sure why I didn't notice it right away because the very first thing I did when the chime stopped working was make sure nothing was getting in the way of the mechanical innards of the chime. I think one of the wires was interfering with the BACK of the plunger and it wasn't visible upon inspection.

I thank all of you for your help, but his turned out to be a very simple issue.