Here's what I have:

A house which was built in 1910, and likely powered by gas alone.
I'm thinking that between the late 19-teens and the mid 1920s, is when they first electrified the place with then-state of the art **** and tube wiring. I suspect that a few additional K&T circuits might've been added, maybe in the 1940s.

Then in 1974 or so, they came in and modernized the electrical service with a new wire drop from the pole, and a GE 70-100 amp circuit breaker box. And they added a bunch of new Romex circuits, which were pretty much all wall-mounted outlets and probably the ceiling lights in the 1st and 2nd floor baths.
At that time, they simply reconnected the K&T from the rest of the overhead lights, and the old baseboard-mounted outlets on the 2nd floor, as was then acceptable.
And of course in the years since then, folks have added new Romex circuits, like when the basement was finished in the 1990s, and possibly the two 2nd floor dedicated outlets for window ACs.

Here's what I've done:
(I turned off circuit breakers until a tic tracer showed no current in these switch boxes.)
Located basement junction box and disconnected two pairs of Romex-fed K&T wires leading upstairs. This took out pretty much every ceiling light on the 1st and 2nd floor, but also a few in the finished basement which are on another circuit. It also killed 3 of 5 baseboard outlets on the 2nd floor. But the tic tracer was still indicating current at some K&T outlets and switches.

Then I located a Romex-fed switch box by the front door, which was serving three K&Ts, one to the porch light, and two to the 3 way switch for the entry room ceiling light. I disconnected them and pulled them out of the box and capped them - and labeled them. Still finding phantom current. Disconnected the K&Ts at the other 3-way switch with no change.

Went up in the attic and located K&T coming out of a junction box, turned off every circuit via the main breaker, and removed that. It turned out to be a single outlet in a 2nd floor baseboard which had been indicating hot, but would not light a lamp. No change to the phantom current.

And sometimes the phantom current would come and go, adding to my confusion! But by somewhat dumb luck, I found out the cause of it! There is a 3 way switched ceiling light in the all-Romex basement which stopped working when I cut the first two lighting circuits. If I flip either of those 3-way switches, it will toggle my phantom current. If I turn off the breaker which powers that light, then there's no phantom current no matter what. And those 3-ways are in a plastic box, with no ground pigtailed to the switches!

My goal is to find where ever this particular circuit is connecting to the **** and tube wiring, and disconnect the daylights out of it, so that no current ever again reaches any of those old wires, and then I will be satisfied enough to call it done, and cut and remove what I can of it. I definitely don't want any current being pulled through them, but I don't want them energized in any way either.

I'm also experiencing this phenomenon on one other Romex circuit, but it is only manifesting at a single 2nd floor baseboard outlet, and I haven't found a switch which affects it.

Then once I'm satisfied with that, I will run new circuits to all of my ceiling lights and switches and the five baseboard outlets, and leave them hanging (extra long and labeled) by the breaker box - so that when an electrician comes and installs a nice new 200 amp box, he can connect them along with the existing Romex circuits I will be keeping. Probably have them install the outlets, switches, and fixtures, too. My buddy is telling me another guy in the neighborhood has the tool to remove the meter, and that I can change my own main box, but I will gladly pay for someone else to do that!

So today I will be looking farther into this. I have found two boxes in the basement near the non-working lights, where the offending Romex circuit passes through, so today I will be disconnecting them, working back toward the main box, to see if that has an effect.

Most people wouldn't go this far to ensure that those K&Ts are dead, but I think it's absolutely necessary.

Anyone have any ideas as to where this phantom current could be coming from? Neutrals? Grounds?

 

look for a hidden fuse box.
when i started rewiring this current house that was originaly built in 1929, i had the same thing. main breaker shut off, but still power to 3 circuits.
once i removed all the sheet rock that was put in in 1974, i found a small 4 circuit screw in fuse box buried behind the sheet rock, but it was still live.
i also found a 2 fuse box down in the basement that powered the furnace and hot water heater.
to avoid problems, i ripped every single piece of wire out and did a complete rewire.
200 amp panel with 100 amp main breaker. 100 amp panel and 60 amp breaker out in the garage. the house has 200 amp two phase service, the garage has 100 amp two phase service.
i also ran 12 gauge wire for the 15 amp circuits so there was no way they could be overloaded.
15 amp outlets and 15 amp breakers, but 20 amp wiring, and no more than 4 outlets per breaker.
the electrical inspector took one look at the main panel and front room wiring and signed off on the rest of the house and garage wiring.

 

Did the inspector see the 15 amp outlets on the 12 gauge wire?

I've been digging in in the basement all morning, and uncovered a(nother) buried junction box! It's kind of wedged into the steel support beam by other wires, so it's going to take more finagling to get it out of there and see what's doin' with it. But much of that time was spent disconnecting a recessed light which wasn't coming on, and a POS old fluorescent fixture which wasn't even secured to anything - just kind of laying across the boiler pipes... Then I removed their wiring back to the switch. I didn't think that would fix the phantom current, but it wasn't a bad thing to do - there was a household extension cord hard wired into the recessed light box! There are 4 or 5 wall outlets near where it was!

If I don't figure this out and get too confused, I can always abandon this basement circuit. The basement was finished out in the '90s, but they didn't do the greatest job, so I'm not too worried about tearing stuff out of there. Still, I have to wonder how many other junction boxes are buried in there...

 

he started to question it, but then realized who i was. my father was fire marshal (chief fire investigator) for 25 years in town, and i was a police officer and volunteer firefighter for 10 years before i was injured in a bad truck wreck.
knowing the reason i did it was that there would be no way to ever overload any circuit, and also the fact that i knew what i was doing he just signed off on all my work without a licensed electrician signing the panel.

 

I've actually had the same thoughts, but have read that you're really not supposed to do that.

But I'm probably not supposed to be doing what I did today, but oh well... So I revisited the boxes I mentioned in my first post, and I kind of found, and definitely fixed my problem! After I removed the recessed light and the florescent light, I went back down and took a look at the box containing the switch to one of the removed lights. I cut out some drywall and followed some wires, and went back to the switch box and removed the 3 way switch, but still got phantom current on the 1st floor switches. So I pulled out the incoming Romex wires, and found that the 2-way next to the 3-way was connected to three different Romex's via pigtail, so I figgered there was a 'pass through' circuit, and disconnected them all. I turned on the breaker and figured out which one was power, turned it back off, and connected one of the two other Romex's. I powered the circuit, and got all my lights back which had been working before. I ran upstairs with the tic tracer and no current! I tried throwing the other 3-way switch by the basement outside door, and went back and checked, and no current! I was super stoked.

Well then I was wondering what that other Romex went to, so I cut the breaker and connected it and powered it back up. This time I had my rear outside lights back, but when I went upstairs and checked the switches, there was current. So I disconnected it, and left the other two connect, and there's been no phantom current!

I do want my outside lights back, but I guess I'll have to isolate the wires from those two fixtures, and run a correct power feed to the switch box. The 3-way will become a 2-way. They didn't use 3 wire cable to do the three way, so it's not worth troubleshooting.

But I guess I will first go after this other circuit which is energizing the wires in a baseboard baseboard outlet. Then I can either tear out all of the K&T which I can, or start stringing new Romex for a bunch of ceiling lights (a few with separately switched fans) and their wall switches, some more outlets, and smoke detectors.

 

good work finding the offending circuit!!!
it sounds like you really need to eliminate as much as possible and run all new legs so the lines are not overloaded.
it is really easy to do with very minimal sheet rock destruction, and an added advantage is you will then eliminate all the hidden junction boxes, extension cord wire jumping between circuits, and other illegal wiring done by amateur butchers.
they you will be assured in the fact the house will not burn down due to some hacks butchering of ther electrical system.

 

OK, so I think I figgered out my stray voltage on this last baseboard outlet! I don't think there was ever a problem! I had positioned a small Fender guitar amp against the hole in the baseboard to block access to the taped-off wires. The amp was plugged into circuit #2, which was the last 'problem' circuit.

I spent all day looking at the wire, which entailed going up in the attic at least three different times! I didn't see anything obvious, although morons had laid insulation over the K&T when I made an attempt to trace it! Found a scrap of the Monday March 3rd, 1958 Cincinnati Times Star. I then came down and probed, and found the 'current' like I expected.

Then I went ahead and unplugged the amp to check its outlet, and left it unplugged. I probed the wires again and nothing! Plugged the amp back in, and the tic tracer lit up like they do when a wire is hot! I tried the test two more times, and that's what it's gotta be.

The thing with the switch plates on the other circuit, #14, was for real though. Maybe I'll dig into the disconnected end of that circuit tomorrow, and see if I can get it sorted out, and get my rear outside lights back.

So now it's time to string some wire to my 1st and 2nd floor overhead lights and switches.

 

This morning I reconnected the feed to the faulty circuit, and started disconnecting and reconnecting everything (one at a time) I could find on the faulty branch. Finally I opened up the switch over the basement kitchen sink, and saw that it was feeding another wire bundle. So I disconnected that, and now no more phantom current!!

Only lights not working down there are the 3-way setup by the outside door, and the two fixtures I removed two days ago - and no more phantom current at the 1st floor switches which are the old K&T!!

So just to update, my **** and tube wiring is still dead!

 

good deal!!!