Doug wrote:
I've got a house that the door chime stopped working (making a chime
noise). I know it's not the outside button and the two wires outside
that connect to the button (that go thru the outside brick wall) when
touching each other showed some spark. One repair guy asked me if
it's a 16v or 24v transformer and I don't know. He seemed to say it's
not a part of the chime box inside. I thought everything was self
contained inside the chime box that mounts on the wall. Is this a
DIY job??? Any good URL to watch on this repair?

Just guessing, 'cause it depends on what king of chime.
If the switch sparks, you've got volts and current, which suggests
it's a solenoid that forces a mass into a mechanical chime.
It's possible that corrosion has increased a contact resistance
so much that it can't move the mass.
But
First thing I'd check is to see if some spider hasn't
gummed up the solenoid so the core can't move and bang the gong.

In my case, the transformer is inside a coat closet above the door
about half way between the button and the chime box.

Never thought about it in that context, but a transformer-operated
doorbell is yet another vampire device that wastes power continuously
when it's used...well...approximately never.