A Postwar Lionel ZW problem

Is it possible that the primary coils are scratched/shorted?

Roger

1 - make certain that the direction/whistle controls are in their "off" position (centered). I have seen ZW's with broken centering springs. 
2 - make certain that there is no debris shorting those controls.

3 - Get a hold of a ZW wiring diagram, and make certain the transformer has not been modified.

C.W.,

I was hoping you'd pop up. Thanks!  I'll check that stuff. I don't think there's a problem  with the centering as they seemed to work perfectly. It seemed strange that only that coil-like wire was getting hot.   And there was only one roller that seemed to have any kind of sparking with it. As I mentioned, one of the original problems with this transformer was that the throttles (all of them) had voltages of up to 4V in the "off" position.         Another question.......is it possible that the coils on the primary are scratched?  Is there a coating on those coils?  

Roger

C.W.,

An interesting thing just occurred while I was checking around in there. Every time (since last night) that I plug the transformer in, that coil-like wire starts to get hot. I did some continuity tests on it and it seemed ok. But then.....it stopped getting hot, no matter the position of the throttles. At that point, I noticed that the breaker bulb was burned out. That coil wire connects to the lamp base. Coincidence?

Roger

Can you post some pictures?

I cannot imagine what that "coil like wire" could be.
Maybe a length of resistance wire that is in series with the pilot light.

Your transformer seems to have multiple problems.
One pilot light (green) should be on when you plug in the transformer. This bulb should be a #51. There should not be any resistors in series with it.

The second pilot light (red) should only be on when the breaker is open, there is a load or short on the transformer, and the control is set to apply some power to the track. The bulb should get brighter and dimmer as the control is moved back and forth (while the breaker is open).
It's that second (red) pilot light that should have the resistor wired in series.

Yes, the green light is always on. Not the problem. The red light was going on intermittently without the breaker tripping. That "coiled wire" as I'm calling it is probably a resistance wire and yes, it is wired in series with the lamp on that side. The 51 bulb on the red side burned out and after that, that coiled resistance wire no longer got hot. I'll post some pictures tonight.

Roger

I have to say.....the other ZWs I've worked on had an actual resistor hooked to that bulb. This "wire" looks like a small diameter long spring. Whatever it is, it looks original.

Roger

Enclosed are two photos of the resistance assembly wire (as per Greenberg). The second photo shows it's attachment to the lamp terminal (shown by the alligator clip). This "wire" has a 60 ohm resistance.  

Roger

The coiled wire looked like resistors I've seen in Lionel product.  I checked a couple of transformers I had handy.
 VW transformer - molded resistor
ZW transformer - as pictured above. It is covered by a woven sleeve.

Still, the red light should not be on all the time. and I don't think there should have been enough current passing through the resistor for it to get hot. Do you have the burnt out bulb? If so, what number is it?

One end of the resistor is attached to the lamp socket terminal.
Where is the other end attached? It should be the "U" terminal (copper strip).
What is the voltage across the OTHER lamp terminal and the far end of the resistor?

C.W.,

The bulb is the typical #51. Going to try and find one locally. 

As I mentioned, the red light was on intermittently. Apparently, whatever was going on in there was not enough to trip the new breaker. But before that bulb blew, the resistor wire was hot enough to smoke. I knew this transformer was going to be trouble when my friend brought it over. I did not like the fact that it had voltage on the outputs with the handles in zero position.  Everything was worn......terminals, rollers etc. I've got a funny feeling it's the coil. All other wires appear to be in their proper places and tight.  

That resistor wire connects to the lamp solder tabs and the other end to the common bar.

Do you want voltage readings at the lamp with the throttles in zero (off ) position? And by "far end" of the resistor, do you mean the "common" bar?

Roger

I've replaced the cord, the breaker, the diodes and all the terminals. I had my friend order all the parts before he brought it over. I still have the replacement rollers, but I'm not going to bother doing them if it's the coil and the transformer is a lost cause. If it can't be fixed, I'll just pull out all the new parts and give them back to him for his parts drawer.  

Is there any way to test the coil to rule that out?

Roger

Roger,    I, too, have rebuilt my two ZWs, new rollers in my VW, and work on other PW transformers.  Questions......

1.)     When you detected 20 volts from the output terms, was it on all 4 ?    Were all 4 throttle handles advanced at the same time ?   Measure the voltage across all 4, one at a time, with only one handle advanced.  Check voltage across all 4, again, as each handle is advanced and remaining 3 are in OFF position.  Perhaps it is only one handle that is always "bleeding" voltage to the output(s).  With the "low" voltage leak add to the proper throttle controlled output, this could account for the higher than expected voltage.

2.)  You can check any secondary coils for "scratching" and loss of integrity with your meter, either measuring voltage as you move the plus side meter probe across the coils windings, or do same with power off, unplugged, using the ohms/continuity check.  Do not know what the resistance reading should be, but check it on each winding coil and compare, see whether one varies in the extreme.

3.)  It is evident there is a voltage leakage to the RED pilot/short bulb, this being the cause of the hot wire, and the bulb burning out.  So, it being voltage leakage, not a dead short, the breaker is not tripped.

4.)  When checking the output terms, check the common side only, with the second probe going to a case ground.  See whether you have any voltage leakage to the internal common ground.  This would account for the constant low voltage output on all 4 channels, and also, for the red bulb coil being hot and premature burn out of bulb.

As stated, I have worked on/rebuilt PW trans myself, never came across this.  OGR put out a video on the ZW rebuild work some years ago, I have a copy somewhere.......   Perhaps if you can find this, it would help with ideas and where to check.

Hope this is some help.....

Jesse    TCA  12-68275 

Do you want voltage readings at the lamp with the throttles in zero (off ) position? And by "far end" of the resistor, do you mean the "common" bar?

Yes, between the common bar and the lamp socket terminal that does not connect to the resistor.
If the lamp lights with the handle off, then take a reading with the handles off.

As I write this, I am wondering whether you have a problem with the insulation between the shafts of the handles and the metal plate on which the red pilot light assembly is mounted. (this is just a guess).
The insulation pieces are shown on the bottom of this service manual page

Jesse and C.W.,

Thanks for your tips. I'll try and get some readings on this in the afternoon. 

I guess it's possible it could be an insulation issue under the lamp socket since when you replace the diodes, all that stuff has to be moved in order to tighten the diode on it's back side. Getting the paper insulators back into position with the "spring" under there is quite the PITA.

Jesse,

Where do you connect the probes when you're doing the coil readings. To each coil winding and.....?

Roger

Couldn't resist going down there and taking some readings (supposed to be mowing the lawn).  Anyway, I assumed that to get readings on the coil wires, I would have one of the leads on the common (U) terminals. And it worked out. I got consistently increasing voltages readings up to 20.67. None of the coil wires produced an erratic reading.

So, I have to check out the insulation under the lamp base and figure out where the the leakage is coming from. I tested each throttle output with the others in off position and there was voltage on each output. I would get anywhere from 2.7 to 4.   Higher on the A and D. I tested my own ZW and had 0 on each output when in "off".

Unfortunately, I couldn't find a 51 bulb locally (auto parts shops). I wanted to avoid ordering just a bulb from Jeff. Maybe I'll just remove one from one of my own KWs or ZW. 

Roger

did you do this one?:

Do you want voltage readings at the lamp with the throttles in zero (off ) position? And by "far end" of the resistor, do you mean the "common" bar?

Yes, between the common bar and the lamp socket terminal that does not connect to the resistor.
If the lamp lights with the handle off, then take a reading with the handles off.

C.W.,

I assume you're asking for a reading on the "red" light side. I've got to find another bulb for that. I'll take one out of one of my other transformers.

Roger

C.W.,

Something weird is going on now. I took a bulb out of one of my KWs and installed it in the Z.  It didn't light up. Took a reading as you suggested. 0 volts.  But, I then shorted the output terminals with an alligator clip.....the breaker tripped, but the light didn't go on. ???

Roger

Oh, and by the way......the resistor wire did not get hot. Another strange development

I just checked a ZW whistle control assembly. The lamp socket is completely isolated from the mounting bracket, so while there would be issues with the insulation being out of place, it would not be exactly what I was thinking.
The base is active in the whistle control circuit.

Something weird is going on now. I took a bulb out of one of my KWs and installed it in the Z.  It didn't light up. Took a reading as you suggested. 0 volts.  But, I then shorted the output terminals with an alligator clip.....the breaker tripped, but the light didn't go on. ???

Did the resistor burn out? Does it still read 60 ohms?

Hmmm......interesting. Well, that narrows the possibilities. 

That was my thought also when the bulb didn't light and I immediately checked the resistance on the wire. 60 ohms. 

Are you certain that the blub you took from your KW is good? Is it a #51?

Yep.....checked it for continuity before I put it in. Not labelled 51 but is marked 6-7+ V

Jesse,

I just realized that I have not checked your #4 in your list.....

4.)  When checking the output terms, check the common side only, with the second probe going to a case ground.  See whether you have any voltage leakage to the internal common ground.  This would account for the constant low voltage output on all 4 channels, and also, for the red bulb coil being hot and premature burn out of bulb.

Tomorrow, when my friend returns,  I'll put the bottom plate back on and then be able to do the "case ground". I had him take the cover and base plate home to do the "grunt work" or cleaning and polishing them.        Sorry I missed that.  I would assume that when I do that test (after the screws are back in), I could just put the probe on the coil support brackets.

Roger

When you perform that #4 check, recommended by Jesse, turn the power plug over 180 degrees and check again. I've had transformers show a problem with the plug one way, but not the other.

Will do. We'll see what happens this afternoon. 

-Roger

Ok.....some mostly good news.   I put the base plate back on, the KW bulb in the socket and reassembled the support brackets etc. Connected it to my test roller track and it controlled a 736 with no problems and no breaker trip. When I alligator clip shorted out the terminal, the breaker tripped and now.....the light went on. And.....the resistance wire did not heat up. I still have voltage leak to all terminals, but it wasn't enough (under 4V or so) to start the engine etc.  Then I did Jesse's #4 test. With the throttle off, I connected to common and one of the support brackets and my meter read 3V.    So, what is the consensus? I'm thinking that the voltage leak won't effect the running of anything.  I still have to replace the rollers, which if we have time, I'll do this afternoon as well.   In any case, I will tell my friend to run this thing with the cover off for awhile to keep tabs on......smoke.

Roger

I don't understand what connecting a lead to one of the support brackets did. The coil support brackets of a ZW are not supposed to be grounded.
Maybe I misinterpreted step #4, I thought the test was supposed to be between the common terminals and a known good ground.

That's what I thought.....the support brackets are connected to the baseplate by the bolts. I wouldn't think that was a ground. But I got a voltage reading.  Other than that and the low voltage reading in the off position, it seems to work fine.  I've got my friend running it with the cover off for awhile.

Roger

Just curious, What kind of meter are you using, analog or digital?

A Fluke digital

I use a Simpson analog meter.    I recall one of the electrical engineer folks on this board explaining something about digital meters showing some sort of residual voltage on postwar style transformers. I don't recall the details or what causes this to happen. Maybe one of them will comment.

You might be able to live with a little leakage from the secondary windings of the transformer. But you want no leakage from the primary windings.  I would recommend that you connect a meter to both prongs of the plug and check resistance to every metal surface in side the ZW. There should be at least one Meg ohm of resistance to anything metal. On a postwar ZW there will be no ground to anything except that the prong connected to the side of the outlet that has the white wire will be grounded at the service entrance to the house.  On this old electrical equipment without a U ground it is always a good idea to use a GFI outlet.  That way if something does go wrong, the 120 volt power will trip off quickly. 

David,

I've got a question about your tests on the prongs. Are you talking 2 tests?  Probe on one prong and the other probe on metal surfaces. And then go to the other prong?

And C.W.,

When I test my other transformers with my Flukes, I get zero voltage off the terminals in off position. My friend's transformer apparently leaks some. 

-Roger

The two prongs of the plug are connected to each end of the same coil, so they should already be connected together.  Just to be sure that there is not a metering problem, connect the two prongs together.  Then one meter lead to the two prongs and the other meter lead to test everything inside the transformer.  This will ensure that there is adequate insulation between the 120 power input and the power out to the trains. 

When I test my other transformers with my Flukes, I get zero voltage off the terminals in off position. My friend's transformer apparently leaks some. 

Did you make the tests with absolutely nothing connected to the output terminals?
From what I remember the "phantom" readings only occur when nothing is connected.
As I wrote earlier, I don't recall the details.

I had a Fluke DMM for a while, but it didn't have the features I wanted, so I passed it on to my older son. One of these days I'll get another.

C.W.

That could very well be about the "phantom readings". I went down and tested a bunch of my transformers and they were all over the map as most of them are connected. When I do get a "phantom", the reading is very low and jumps a bit. I know to ignore it. But one thing I did notice just now was that my test transformer (my childhood first transformer......1033) reads 3.4V with nothing connected. So that one has more voltage leak than my friend's ZW. Never noticed it as whenever I clip it to a test track, there is no response by the engine when it's in the 0volt position.

I started out with a Sperry DMM, but it didn't have auto ranging and involved too many steps to get readings. Over time I moved on to 2 Flukes (my main one has a huge range of features and the other is a clamp-on for my amperage readings). Love them both. 

Roger