Smoking KW Transformer

Did it smoke with nothing attached to the terminals? If so, then I am curious about the history of the transformer. Do you have any idea of who may have worked on it in the past?

My semi-educated guess is that there is a short in one of the secondary circuits that bypasses the internal circuit breaker.

If it only smoked while being connected to your trains, then I would still suspect a short bypassing the internal breaker, but the cause would be external. The Lionel service manual states explicitly:

quote:

Note that the circuit breaker does not protect binding post combinations A-B, B-D and C-U

I guess the most likely combination for an accidental short would be C-U. This could happen on a block control layout where someone connected C to the outside rail in one location to get a lower voltage range (0-14) and connected "U" to the outside rail in another location (that was electrically connected) to get a higher voltage range (6-18) volts.
The internal breaker would not interrupt this circuit.

I'd look very closely at the top of the coils where the rollers ride.  I'm guessing that at least one coil turn is shorted where they are bare and that is causing excessive current in the coils.

O.K., I think I know what to look for but how do I rectify the problem?  Is it just a question of replacing the rollers? 

If the coils are shorted, you have to try to "unshort them.  I had one like this, I stuck a non-metallic blade between the coils to separate them a bit, then put enamel on the side of the wires again.  I also smoothed the rough spot that was probably the cause.  It's a bit tricky, but other than scrapping the coil, that's the only thing you can do.

It should be pretty obvious if they're really shorted, just look closely with a eye loupe.  You will have to take the top switch plate off, so exhaust other possibilities first.

Fascinating.., I can't seem to understand how two adjacent loops of a coil that are touching could cause smoke.

Thanks gunrunner, I'll give that a go.  Like I said before I checked it out pretty closely and all of the connections are good and everything is connected where it should be.  However, I did not pull the the top switch plate to check the coils. 

Really?  What happens if you short the outputs of a transformer without a circuit breaker in the picture?  Things get hot.  You're doing the same thing, only with one coil!  That coil will get VERY hot real quick.  If you don't believe it, just stick a screwdriver across adjacent loops in any Lionel transformer and let us know what you see.

O.K. gunrunner I pulled the top switch plate and scoped out the coil very closely and I didn't see anything really out of the ordinary other than the fact that the top of the coil was pretty dirty.  I also noted that one of the contact arm assemblies which holds the carbon rollers in place was a little bent and it appeared that part of the assembly other than just the roller was rubbing against the coil.  I straightened it out and cleaned the coil off with a clean ink eraser and wiped it down real good.  I then re-hooked everything back up and put the case back on.  I then decided to test it and ran a couple of different engines with varying consists for about an hour at various speeds with no apparent overheating occurring.

Afterwards when reading my repair manual I noted that it states to keep the surface of the coil clean.  Could this have caused it to overheat?  Or is it possible the contact arm rubbing against the coil caused it?  Or perhaps both?  Regardless of what it was why didn't the circuit breaker kick in?  I am still a bit leery of this transformer.

The Primary and secondary coils are before the circuit breaker. If the current in the secondary coils is excessive because of a short out on the track then the breaker comes into play as current is flowing through it. If the short is internal then the current is not traveling through the breaker circuit. Yes dirt can cause this but primarily the wiper arm touching the secondaries causes more than one place of contact. That was more than likely the problem. Also on these older transformers the breaker could be non functional or set to high. I personally rely on fuses to protect the transformer and things that may short out on the track.

  Ron

I'm not sure what you mean when you state you are using A1-U2 posts on the KW. To simplify things just use the A post and the U post which are on the same side of the terminal plate.  This will run an engine using the A control lever.  On the other side of the terminal plate use the B post and U post.  This will run an engine using the B control lever. 

Sounds like you probably found it.  If the arm was rubbing and allowing the roller to roll on the coil, that's a real problem!  Contamination on the top of the exposed coil windings would easily short things as well.

Keep an eye on it, but it sounds like you are onto the solution.

As previously stated, the circuit breaker only protects for outside loads, you were putting a load on the transformer internally, there was no current path through the circuit breaker in this case.

Ok let me see if I got this right.  One Wire from A post attached to track plate 1 then two wires attached to U and and B attached to track plate 2?  That right?

I have seen this problem before mayself. The smoke was likely coming from the primary side. Has the coil wrapping paper turned brown, like burnt? There is no real repair, unless you replace the whole coil assembly. Probably not worth the effort, unless you have a spare coil assembly. KW's can be replaced fairly inexpensively.

Sounds like it might have been a shorted secondary in this case.

The coil wrapping did not turn brown like it was burnt.  As I previously posted the KW with a little well directed tinkering via the gunrunner seems to be working fine right now.  However, I am going to watch it closely.  Thanks to everyone for your highly valued assistance.

If you have only one loop of track and you are only operating one engine you take your hook up wire and attach one end to the A post on the transformer and the other end to the track lock on clip marked 1.  You take another piece of hook up wire and attach to the U post located just above the A post.  Then take the other end of this wire and hook it to the track lock on clip marked 2.  Your engine should now move.  Be aware, however, often times when you use the whistle controller to sound the whistle your engine may slow down a bit and the lights may briefly dim.