Home automation is the residential extension of building automation.
It is automation of the home, housework or household activity.
Home automation may include centralized control of lighting, HVAC (heating, ventilation and air conditioning), appliances, security locks of gates and doors and other systems, to provide improved convenience, comfort, energy efficiency and security.
Warning: Working with electricity can result in injury, property damage, or even death if it is not done properly. Please keep this in mind while assisting others. If you are not sure about what you are doing, hire a licensed professional.
Short (hah) of opening the box to verify it’s just a transformer and not some other system I don’t know.
But if the previous owner didn’t specifically exclude the Ring doorbell from the listing, they are required by most law (assuming you are US) to leave it. Even if they did exclude it, they are usually required to replace it with a working alternative. In either case you can take the cost of repair out of their escrow.
Disconnect bell wire wire from transformer and measure voltage at the screw terminals. Should be 24VAC. If nothing, internal fuse link in transformer is open. Transformer is toast.
Tested and it is dead. Time for replacement
Well the good news is they are pretty cheap.
It will be impossible to answer some of your questions accurately, based solely on the information that you provided. We don't know exactly what you have or even what county you're in.
Did the transformer fry?
It is a real possibility. Burning smell bad. But, we can't be sure. Someone with expertise will be able to test the transformer with a multimeter and know if it is good or bad.
Is it common to be wired to the main?
No it is very uncommon. Absolutely nothing, except branch circuit breakers, should be wired to the main breaker. I would guess that you missed something, possibly a sub-panel. But, if the light and transformer are indeed directly connected to the main breaker, then someone has done a terrible (DIWHY) wiring job that would be illegal in many countries.
The Ring door bell requires a special resistor when being powered by an AC doorbell. This is discussed in the installation instructions. I'm guessing that this resistor was not in place when your friend did the installation. But, again I cannot know for sure.
My opinion is that your friend does not know enough about this to do the job. My opinion is that you should hire an electrician to:
Identify the breaker you could not find.
Test the transformer, and replace it if needed.
Install the door bell correctly and determine if the Ring itself was fried in all of this misadventure.
I would worry less about the doorbell and more about the fact you have a live circuit branch in your house you can't turn off. Get someone in the house to find out what that's about before you try and replace anything.
Some deeper hunting found the issue and it has been corrected. Crossed on 2 breakers so when one was off it was still getting power.
Nice job. I'd say the doorbell issue did you a favor...
Doorbell transformers are cheap (20 bucks at home depot).
Thank you. I should have handled the install myself. I am fairly handy (mostly carpentry and drywall) but I can figure my way around things. Sadly I was busy hanging tvs and thought he was capable. I was wrong.