What is going on with my doorbell?

My wife is complaining that the rear doorbell is not working. Actually it may not have worked when we bought the house 12 years ago, so I can't imagine why it matters now, but that's another story.
The chime has three terminals on it. A white wire goes to "front", a red to "transformer" and a black to "rear". The panel has two transformers on it, each putting out 20vac to sets of white and red wires. Each switch (or whatever the pushbutton is called) has a red and white wire on it. There is 20vac at each switch.
The rear doorbell does not chime when I short the switch.
I cannot figure out: 1) where the black wire at the chime comes from, when there isn't a black wire at either switch or transformer 2) why I have two transformers when seemingly only one is needed for the system 3) why the rear chime doesn't work when there is voltage at the switch and the front chime works
Any idea what is going on here? Is there any other use for a 20vac transformer but a doorbell? (The wires from the transformers get lost in the walls, but one goes to the middle of the house by the front door and the other goes to the far end of the house by the rear door.)
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I tired to email you some suggestions but I got an error saying that there is a permanent failure with your address.
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wrote:

I never check that account, so it is probably full. What was your suggestion?
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T > My wife is complaining that the rear doorbell is not working. Actually it T > may not have worked when we bought the house 12 years ago, so I can't T > imagine why it matters now, but that's another story.
Uh-huh!
T > The chime has three terminals on it. A white wire goes to "front", a red t
T > "transformer" and a black to "rear".
Seems like red and black for the doorbells and white as the common would make a little more sense.
T > The panel has two transformers on it, each putting out 20vac to sets of T > white and red wires. T > Each switch (or whatever the pushbutton is called) has a red and white wire T > on it. There is 20vac at each switch.
Which means there is a complete circuit. What happens when you press the doorbell? I'm thinking the meter reading should go to zero as the closed switch would provide a lower resistance pathway. (Probably no need to do this as you said later you shorted out the switch and still didn't work.)
T > The rear doorbell does not chime when I short the switch.
What happens if you temporarily swap wires between the front and rear terminals (your white and black)? ...Seems like red and black for the doorbells and white as the common would make a little more sense.
T > I cannot figure out: T > 1) where the black wire at the chime comes from, when there isn't a black T > wire at either switch or transformer
There is a junction somewhere. Ours is in the basement next to the wall and a duct pipe with a lump of friction tape holding it all together. (I didn't install it that way!)
T > 2) why I have two transformers when seemingly only one is needed for the T > system
Good question. A higher current-supplying transformer is necessary for multiple door chimes (first floor, second floor).
T > 3) why the rear chime doesn't work when there is voltage at the switch and T > the front chime works
Wired wrong (see my comment on white as common)?
Is there voltage present at the rear door/common terminals? If a mechanical plunger does it work by hand or is it possibly stuck (gunk build-up)?
- barry.martinATthesafebbs.zeppole.com
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