Lionel Classics Blue Comet 400E Motor Diagnosis / Repair

Do the brushes have the braided wire tether. If so, I’ve seen the tether keep the brush from making contact. Make sure the tether is not hung up on the brush tube.

steve

Hey Steve, typical brush and brush spring combo. I checked just to make sure and all is making good contact.

The loco has a Bild-A-Loco motor and does not need the wheels pressed on, they just lift out. On one side, look for tubes with a slotted screw head on the end. Undo those screws and the brush and spring will come out. Ensure the brush is clean and spring is not compressed. Replace if neccessary.

If you need to check the E-Unit remove the main rods, look for the levers holding the motor to the frame and turn them and carefully lift the motor out. There will be a lead for the lights attached. Once you have the motor out, remove the e-unit and clean it. The drum is most likely tarnished.

Tin

I realize this is of no help,but,,,,,mind did the same thing a year after a bought new,i took it to a service station at the time,all they said was loose wire,,,so,it seems its a rather common problem 

Tin, 

Thank you for the insight! Once I figured out to drop the bottom plate, it became a piece of cake to pull it apart. So moving forward I disconnected the E unit and tried to run the motor and just got a buzz but no movement. Pulled the armature and ohmed it out at 1.0 on all three faces with the unit testing good for not shorting to the shaft. Makes me suspect that it is the field. Can someone tell me the correct way to test the field on this unit? 

The good news is that if the field does test bad, that Smittys appears to stock a replacement. 

Thanks again for the help, 
Derek

Unfortunately just checking the resistance of either the armature windings or the field coil will not reveal a shorted coil. A shorted coil will not change the resistance reading significantly to identify a short.

To properly test a coil, it needs to be tested with a coil "ringer".

Chances are the field coil is good.

Here is a basic wiring diagram of a motor with an E-unit. Check your wiring against it.

Larry

Well another night on the work bench and I'm still stumped. E unit cycles just fine so I unwired it to direct test the motor. Put hot to the top of the field coil and then jumped the hot to one brush, the other side of the field grounds through the frame and then if I ground the second brush to the frame it just sits there and vibrates. I'm lost on this one and would like to get it up and running ASAP. Any more ideas fellas? 

Thanks,
Derek

Try 'The Motor Doctor'

Albert Garlatti, PO Box 91, Harrison, OH 45030

513-399-4035    motordoc@themotordoctor.com

He is good and reasonably priced.

bruce

To test the motor, jumper one brush to the field, attach one transformer lead to the frame, the other transformer lead to the other brush. The motor should operate in one direction.

The e-unit, if it has been inactive since the 80's when this loco was made, probably has oxidation on the drum since they went to bare copper drums in lieu of the nickel plated ones used in postwar.  I remove the drum to clean it, but it can be cleaned in place.  Sight into the 4-fingered side of the e-unit and advance the drum by hand.  Note if the center two fingers make contact with the copper sections of the drum.  If not, the fingers may have to be adjusted to make contact.

Notch 6 posted:

Well another night on the work bench and I'm still stumped. E unit cycles just fine so I unwired it to direct test the motor. Put hot to the top of the field coil and then jumped the hot to one brush, the other side of the field grounds through the frame and then if I ground the second brush to the frame it just sits there and vibrates. I'm lost on this one and would like to get it up and running ASAP. Any more ideas fellas? 

Thanks,
Derek

Correct me if I read that wrong. It sounds like you are wiring the field and the armature in parallel, when they must be in series.

Try like this

-E-unit not connected to the motor

-transformer hot to one brush

-the other brush to the end of the field that does not go to ground

-the other transformer lead to the frame

That should make it run.

Roy is right. Brush #1 to roller power, Brush #2 to field #1, then field#2 to chassis.

  The only other time I've encountered that was an unkowing attempting to run a DC only motor on AC. I know motors in general well enough, but not pre war. I only know there were SOME open frame but dc only motors in trains during the pre war era. I don't have a clue on mfgs., or appearance, etc.

Well thank you all for the replies! After getting the wiring right I was able to diagnose that for some reason the field coil was not grounding properly. A small additional ground wire from the coil to the frame and the engine runs like a top. I’m so excited to have this running for Christmas this year. Thank you all for your help.

Another common issue with LTI, they bundle the wires with wire nuts. On occasion the wire nut is not installed correctly allowing for a loose connection.