I want to explain the situation with these transformers, then have a few questions. Hope you can take the time to read through this. Always enjoy the advice from this forum.
Decades ago, I inherited lots of Lionel O gauge items, including one each of a type R and V transformer. I have a PW ZW that I use for track power and some accessories, but needed another transformer for accessories only on a layout I am building, so I put the V into service. I did some cursory updates: new face plate, greased upper gears, cleaned upper coil and carbon rollers, etc, but did not access the lower coil. In order to do that I had to remove heavy wires from their lugs, and did not want to jeopardize the unit with my limited soldering skills. All seemed fine, except that when I engaged the AU circuit, the transformer began to overheat, so I quickly turned that circuit off and did not use it. For several months all worked fine on the other 3 circuits, until last week. I must have nudged the knob on the AU circuit, b/c suddenly the unit began to smoke, overheat, and emit a terrible burning odor that pervaded the entire basement. I quickly shut down the circuit and unplugged the unit. Had to remove it from the house b/c of the odor.
After it cooled, I opened it up to take a look. Upper unit looked fine, but all I could see for the lower unit was that the carbon rollers were not rotating when the knobs were turned and the arms holding the rollers seemed discolored. I debated on removing the soldered heavy wires to access the lower unit, then decided to hold off. After a few days, I put the transformer back in service, and although the other circuits seemed fine with no overheating, the odor reappeared, so I had to again remove the transformer.
I then turned to the R transformer. I had previously replaced the face plate thinking I would sell it, but now needed it to operate the accessories. Opened it up and did some minimal cleaning. Seemed in good shape. I was about to attach bus wires for accessories to it, then realized I had to put it in phase with the ZW first. So here are my questions:
For type V:
1. Is it worth attempting any repair? Should I remove the heavy wires to access the lower unit?
For the type R:
1. Given that it does not appear to have a single "common ground" terminal, is it possible to put it in phase with the ZW? If so, which terminal should I use on the R unit to connect to the common ground on the ZW? (see photo)
2. Is it possible to continue to use the single bus wire I have for ALL track and accessories with the R unit, or do I have to use different ground wires for different levels of fixed volt output, as well as both variable circuits? If I must use different ground wires, how does the effect phasing with the ZW?
Final questions: Should I seek another transformer entirely for the additional accessories besides the ZW? If so, which one? I really do not need the modern high-end units for my accessories, but I do need a unit that can provide different voltage levels for different accessories, of which there are lots of vintage Lionels, like the lumber loader, log loader, sawmill, coal ramp and loader, milk car, cattle car, rocket launcher, 2 magnetic cranes, bascule bridge (actually, it's the modern version), lamps, gatemen and crossing gates, 13 switches, 5 UCS tracks, and 5 bumpers (switches, bumpers, and UCS tracks powered separately from track power).
Many thanks for any advice,