Help with Servicing a Pre-war Lionel Multivolt Type T 100 Watt Transformer

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

@harmonyards posted:

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

Thanks Pat.  It's ok, I didn't inhale.

Seriously though, PPE is a good idea.