One like this belonged to my dad, and I have it, although it lacks the sweep arm to change voltage. At one point I had the lettered posts connected to a rotary switch and used it as a yard cab, but it didn't really have enough juice for that. I've never taken it apart, but look forward to hearing about your progress with it.

I have worked on a number of the prewar multi volt transformers.  I do not recall if any were specifically the T, but I think they are similar.  The top does not come off, it just folds back. It is tight working in side. As I recall the cord is spliced to the magnetic wire that the primary coil is wound with.  The splice is taped.  There may be a lot of asbestos sleeving in side.   The problems I have had are there is little room to work and nothing is marked. All of the copper is corroded black.  Cleaning it prior to soldering can be difficult.

Prior to changing the cord, even prior to dissassembly, check for resistance between the prongs on the plug. There should be little or no resistance. Then check the resistance between the prongs on the plug and all of the terminal posts and the case. One Megohm or greater would be nice.   If the transformer does not pass these tests, there is probably no reason to go any farther, unless you can verify the problem is limited to the cord that is going to be changed.

@SteveH posted:

...Ok, before you say it, yes I know many of you may be thinking "Why would you want to mess with this death trap, use a modern transformer?" or "Just put it on the self to look at." To answer these first, let me say, I like bringing old things back to life and I have a healthy respect for, training, and experience with electrical device repair.   This unit seems to be in relatively good condition and I'd love for it to be actually working and not just a static display piece.  I also plan to have it's output running through a 5 Amp Airpax Instant Breaker.  If I can replace the cord and get this to where I feel its relatively safe for adult use, I may use it for accessories.  When finished, I plan to connect it to a Variac and gradually raise the input voltage to ensure that there are no internal shorts or voltage leakage....

Thank you for a) wanting to do this, b) clearly stating your background and qualifications, and c) being cautious. IMO, too many folks (probably including me at one time) open up old transformers without understanding the risks and pitfalls.  Having seen many of your previous posts on electrical topics, I'm confident that you'll have a good outcome.

There are copper wires everywhere in there, covered with tar or a similar substance as noted previously. You will find it a mess. If you are going to remove the transformer coil, be sure to mark where each wire goes. Best of luck.

@David Johnston and @Chuck Sartor Thank you for the tips and suggestions.

Resistance between the 2 power cord prongs is near zero, as it should be.  No measurable resistance (2MΩ setting) between the power cord prongs and any of the terminals or wiper arm.  So far so good...

@Ken Wing and @Mallard4468 Thank you for the encouragement.

After the resistance checks, I opened it up.  I was pleasantly surprised to find that this one has no tar like substance inside.  The windings are actually coated with shellac.  Maybe this one was made towards the end of the pre-war era?

Everything actually looks pretty good inside for being at least 85 years old.

Here are some pictures of the insides (click to enlarge):

After tightening the loose retaining nuts on the binding posts, I looked online and ordered these items to replace the line cord:

Cloth covered 18/2 cord

and

Retro look non-polarized plug

Once these parts arrive, the rest should be fairly straightforward.  Thanks again for the assistance.

I recently opened an old Jefferson transformer that needed a cord change and found it potted in asphalt. It is repairable, but it is a summer time job that needs to be done out of doors.

@David Johnston posted:

I recently opened an old Jefferson transformer that needed a cord change and found it potted in asphalt. It is repairable, but it is a summer time job that needs to be done out of doors.

Nice!  What's your plan for dealing with the tar?  Heat gun, warm sunny day, both, other?

I use a heat gun and run the tar into a metal bowl so I can heat it and pour it back in when I am finished. But everything is still tar coated, so time with a strong solvents and a rag is required. Best advice is not to burn down the house.

Good advice   If you get a chance, I'd enjoy seeing some pictures of the guts after the tar is mostly removed.

Steve, ….one thing I know about these, and David touched upon this, they do have  asbestos inside them, …..I believe the sleeves are 100% asbestos, …..when you get to them, try not to make them into dust,…..do use the proper PPE buddy!….we’d like you to stick around here for a while!!……😉

Pat

Success!

Well, it's been almost 2 years since I started this project, but it's essentially done now.  It only took a few hours to do the actual work and find parts.

Here's what it looks like now:

For anyone interested, here's a summary of what I did and some pictures that may help others working on similar pre-war Lionel Multivolt transformers.

Lionel Type T Multivolt Transformer Repair Notes:
Due to the possibility of asbestos, while wearing a respirator, I clipped off the original line cord and discarded it along with the brittle Bakelite wall plug.

Next, I tested the primary and secondary coils for continuity.  So far so good.

Bought a new 18-2 stranded line cord with cloth cover (woven over PVC jacket) and a modern vintage looking non-polarized plug.  Cleaned the top panel wiper contacts & porcelain insulator, then after stripping and tinning the wire ends installed the new cord and plug.  Note the strain relief knot, 12 gauge solid insulated wire wrap and heat shrink tubing.

Tested the insulation on the windings without any loads connected to the secondaries.  Using a Variac, slowly brought the input voltage up to 130V AC input to ensure no shorting.  I kept an eye on the ammeter to ensure no current was flowing during this test.

Tightened Output binding post retaining nuts on the top panel.
On the inside of the top panel, the variable (wiper) contact post internal nuts were especially loose and in some cases not making good electrical connections.

At 120VAC input, tested all secondary fixed and variable outputs and verified correct the correct voltages were present.

Using resistive Loads, I tested the outputs one at a time up to 80 Watts each for about a minute, with no noticeable heat or unexpected sounds coming from the transformer housing.  Under load the measured voltages dropped a bit as expected.

Since it wasn't obvious at first, while reassembling I needed to use the original dis-assembly pictures I took, to find the correct locations within the lamination stack where the core support brackets were supposed to be so that everything had the correct clearances inside the housing.

For anyone doing this, make sure that the 2 horizontal pieces of cardboard are put back in between the backs of the terminal screws and the secondary leads to help protect the shellacked cloth insulation on these wires.

The next steps in the assembly were to reinsert the fragile cardboard that wraps around the four sides of the core and secondary wires and carefully fit the assembly back into the housing.

Before bending the 4 retaining tabs back onto the top panel (not wanting to stress them with multiple bendings), I temporarily zip tied it in place and did one more electrical test of everything to make sure there were no issues caused by the reassembly process.  One verified, I bent the tabs back down and removed the zip tie.

Now it's essentially done except for some possible cosmetic finishes.

It's still missing one of the Binding Post thumb nuts.  Although they're not an exact match, I'm probably going to get some Repro-Nickel replacements from Trainz.  Link here: https://www.trainz.com/products/lionel-1033-47-6-32-fancy-nickel-binding-post-nuts-fits-1032-1033-lw?variant=43592738013306

Maybe at some point I may try touching up the white lettering, but my fine detail painting skills aren't great and I don't want the lettering to look blotchy.  Besides, other than being difficult to read, I kinda like the well used look it has.  If you have any lettering touch-up tips to share or have an original prewar thumb nut to spare, that would be great!

When I use this, it will only be occasional and while closely supervised. For added safety, I intend to plug it into a fused 1Amp supply circuit.

I want to again thank all those who contributed their knowledge and experience here and hope this Topic may be of some help in the future to others.