Lionel 397 Coal Loader motor

Up front, I am not a lionel motor expert.

The dark spots on you cleaned armature contacts indicate to me that at least one of the windings is shorted. I believe I am correct in the following:

With armature removed from motor, try:

Number the three armature contact plates 1, 2, 3. Use an ohm meter to measure the resistance from 1 to 2, 1 to 3, and 2 to 3, writing their values down. The values will be low, but should be about the same.

Also, measure resistance from 1 to armature shaft, 2 to shaft, 3 to shaft ==> I believe these three should should open circuit.

Hopefully others will have better advice or more info to help you, but the above should be a good start. Report your results so others get all the info.

Good Luck!!!

One of the brush springs is almost 2 x the other.  That means one may not be applying enough pressure for a good contact.   If the spring is still good and not corroded, it can be stretched longer to match the other.   Careful, too much spring force can add drag. 

I would make sure the ends of the brushes are clean of buildup.   Very fine sandpaper or a Rush Eraser type tool can be used to clean the brush plate. 

With the CB tripping, I would lean toward a short. in one of the windings.   Also check the winding on the field coil.   One end connects to one of the brush ports and the other usually to ground.   You need to disconnect the end from the ground and then do a continuity check between the winding and the casing of the field winding. 

Are there any discolored areas on the windings?   This could point to high heat or a short.   Also smell the windings.  You are looking for the burnt wiring smell.

Rush Earaser

MED:  I get 1.5 ohm between all 3 of the faces on the armature and all 3 are OL if checked direct to the shaft.   I stretched the one spring to equalize length and it still just buzzes or stutters, no spinning but it is smoother now than before.  Still will not rotate so I am out of ideas.  There is no discoloration or dirt between the faces.  It looks as good as any Lionel motor I ever worked on!  Any other ideas?  The value of this item is not worth spending the money on a new motor that's for sure. I am already in too deep with the shaft parts I need!  Oh well live and learn.

Did you also check the field coil winding's end to end resistance as well as for it possibly shorting to the motor housing?

Is it wired correctly?  It sounds like the armature and field are not in series.

To help you with checking the wiring as suggested by @David Johnston, I am including a schematic.

Do as @SteveH suggested and measure resistance of field winding, and please post results.

Once you verify the wiring is correct, and motor still won't work, I would check how freely you can rotate the armature of the motor assembled with the brushes. You should be able to turn the armature a full revolution with very minimal force - if trying to rotate the armature is very stiff, you may have too much brush pressure (springs too long) to allow easy rotation.

My fear is that there is a short within the field winding (not a short to the motor case, but a short from field winding wire to field winding wire. This would result in a reduced magnitude of the magnetic field the field winding is supposed to create.

Dave I have that unit and if you would like bring yours over and we can compare them. Mind I bought mine maybe 20 years ago but have never used it or tested it. I bought to go with my coaling ramp(that has been  family owned since new).

Sorry to be a bit late with this, but thanks for the all the input.  I determined the field winding must be the problem and if that is so I just need a new motor, which is not worth the cost unless I find a real deal.  I may mess with it some more when I have the time.  I don't have a layout so this was going to go to a garage sale for Foxdale Village in State College next spring.  It's a retirement place.  Like I said, the armature checks out ok and rotates freely and the brushes are fine.  The motor itself looks excellent so this problem really surprised me.  Ones on eBay all look well used and dirty.  Thanks again for all the input.

I finally checked the resistance on the field coil and got 2.4 ohms!  So there is no short there, unless the reading is incorrect.  What should a field coil read?   If the reading is good what is causing the motor not to spin?  Thanks again.  

I am at a bit of a loss - the 2.4ohm field DC resistance would seem okay to me.

I will assume that you used the schematic supplied earlier to verify motor is wired correctly.

Another place that can also be measured is the resistance from one end of the field wire to the plates that the field wire is wound around, but this will take a little more effort in that you have to have both ends of the field winding wire disconnected from the motor. So if you want to unsolder one end that is to the motor housing, then do the measurement, the reading should be open circuit.

Did you clean the inside of the "tubes" the brushes go into as they contact the armature? If these are still very dirty, retry motor after cleaning them.

I would try the following - put the brushes in the "tubes" but do not "clamp" them down. Using two fingers (bandaid on each finger tip to guarantee no shock or heat burn), one for each brush, gently push sideways and down to make contact with the tubes and armature plates. Other hand to apply and remove power. I know this sounds a bit like desperation, and it is - but without an identical motor to try swapping armatures, I at the end of my knowledge base.

Assemble it and take pictures of all of the wiring. It sounds like the field is in parallel with the armature instead of in series.

I have a couple of these and have restored them.

Looking closely at your photos, is there something missing from your brush plate?

Left is yours    right is original

Hopefully to add some additional info to that @EscapeRocks posted, which looks like the problem - missing contact plate to get power to one of the brushes..

I have used the pic posted by @EscapeRocks to try to make the below schematic as to the way it should be.

This problem does not fit with the symptoms.  “The motor hums and buzzes but the armature does not spin!”

So one more way to look at this motor and see if it is wired correctly.

Refer to the schematic and one of your original pics - I added reference letters to both to aid in my writings.

Do these measurements with brushes removed (motor can be assembled as long as brushes are not installed.

The resistance from the loose end of Wire A should be 0 ohms to the inside of the brush "tube" Wire A is connected to.

You pic shows Wire B from the field unsoldered from the brush plate - if still unsoldered, the second brush "tube" should be 0 ohms to where the field Wire B will be soldered to. If Wire B has been resoldered to the brush plate, the measurement is still the same, brush "tube" to Wire B should be 0 ohms.

Wire B to the case of the motor I marked as C should be the 2.4 ohms you reported you measured in a prior post.

Measure from brush tube to brush tube - should be open circuit.

So in words, the power of a working motor would flow from Wire A to its brush tube, via brush/tube to armature, through armature to other brush tube, from this brush tube to field via Wire B, then through field to the motor case C, motor case C is return to power source.

One other thing. Where was Wire B soldered on the brush plate??? I believe that as @EscapeRocks posted, your motor is missing a contact plate from one of your brush tubes, the contact plate to which Wire B would have been soldered. However, the symptoms you posted makes me think some former owner may have realized the contact plate was missing, and decided as a fix to solder Wire B directly to the top edge of the brush tube, bypassing the missing contact plate.

@MED posted:

One other thing. Where was Wire B soldered on the brush plate??? I believe that as @EscapeRocks posted, your motor is missing a contact plate from one of your brush tubes, the contact plate to which Wire B would have been soldered. However, the symptoms you posted makes me think some former owner may have realized the contact plate was missing, and decided as a fix to solder Wire B directly to the top edge of the brush tube, bypassing the missing contact plate.

@MED    

I like your train (no pun) of thought here.   Also, if a former owner did attempt to fix it in the way you hypothesize, it may also account for the that one spring being so compressed compared to the other.

My brush plate is not missing, see photo.  
First photo was not a good shot.  I have cleaned the brush tubes, windings etc. Motor still does not run.  Thanks for all the help but Im done with this.  

@pennsydave posted:

Motor still does not run.

@ADCX Rob posted:

Assemble it and take pictures of all of the wiring. It sounds like the field is in parallel with the armature instead of in series.

Please post pics fully wired / assembled. This may tell the story.

Just out of curiosity have you tried loosening the screws on the two halves and trying the motor?

John

Craftech:  Do you mean loosening the screws that hold the brush plate to the moron frame?  

ADCX Rob:  OK, I will reassemble and resolder and take some photos.  Will probably be later in the day.

I am amazed at how much you guys are willing to help!  I know it's tough to troubleshoot when you can't really see the problem and trying to decide if the 'poster' is giving you good information!

@pennsydave posted:

My brush plate is not missing, see photo.  
First photo was not a good shot.  I have cleaned the brush tubes, windings etc. Motor still does not run.  Thanks for all the help but Im done with this.  

Ahhh okay.   There it is

Sorry for the frustration - yours for doing all these tries and not getting the motor to run, and mine for not being able to help you.,

I found this pic online of a wired 397-M motor and added my A,B,C references I used in a prior post. A is wire from power source to Brush, B is where one end of field is soldered supplying power to the field winding after power passes Brush-Armature-Brush. C is where the other end of the field winding is attached to the case, and the case gets connected as return to the power source.

Yes, that is exactly how mine was wired.  I even reinstalled the motor thinking the base plate would help provide a better ground, and still no improvement.  I also get small flashes of spark at both brushes on the commutator.  It just seems like it should work!!  Again thanks for all the inputs from everyone!  OGR Forum is a great source of help and information!  

@pennsydave posted:

Craftech:  Do you mean loosening the screws that hold the brush plate to the moron frame?  

Yes,

John

Its alive!!  I put it back together and now it works!!  See video.   Thanks to everyone who helped make this happen!  OGR people are 😊 Thank you.

@pennsydave posted:

Its alive!!  I put it back together and now it works!!  See video.   Thanks to everyone who helped make this happen!  OGR people are 😊 Thank you.

Great News !

Tell us.  What finally fixed it?

John

Congrats! Always makes one feel good to solve a problem!