Hi guys,

Check this video

https://youtube.com/shorts/H0kJ7ou9GE8

So one of my locos stopped running. The motor was actually quite new because I converted this from Delta little over 6 months ago.

From the beginning there were times when the loco seemed jammed but started running with a little push. I thought there was something in the gears. Gears move freely thou, without the motor.

So now the loco won’t move anymore. Sounds and lights work thou so decoder should be fine (gonna try to drive some basic DC motor later on thou)

Funny thing is the motor feedback… If I push the loco on the rails, I cam hear chifs and when I push it the other way, I’ll hear squealing brakes.

Anyway I pulled the motor out, took my Märklin Z DC speed controller and tried to power the motor. Nothing but sparks.

So I guess I need a new armature?

BR,
-Eino

Hello Eino,

I'm a bit confused by your video as it looks as though the motor parts are not in the chassis. The casting of the chassis has the bearing that supports the other end of the armature. The motor won't run unless the magnet, armature and motor shield are assembled into the chassis as the armature will simply jam against the magnet. With these older models the casting of the chassis forms part of the motor.

However, since you say the loco wasn't running correctly before taking it apart there must be something wrong.
Remove the brushes and the motor shield and the armature.

First check the brushes, I have had a bit chip off resulting in a pointed edge that would catch in the slots of the commutator. Have a look and make sure the ends are intact. I've only known this once but it's an easy check. They should have a nice curved inwards shape on the inner end.

Then check the armature for any signs of overheating. Sometimes this can show as scorched windings. Then look at the commutator. I have had one where one of the segments actually became detached causing the loco to lock up.

Give the parts a good clean paying particular attention to cleaning the slots of the commutator with the tip of a scalpel blade or toothpick or something similar. I had a loco just last week that suddenly stopped and there was a tiny speck of something conductive in one of the slots. I picked it out and it was fine.

Do you know how to check an armature electrically with a multi meter? If so that's always a good check as it'll give an idea if there are open windings or shorted ones.

With the motor parts out of the chassis check the chassis to make sure the wheels turn freely in both directions with no stiffness or locking up.

Finally reassemble the magnet, armature and motor shield into the chassis and try turning the wheels again to make sure the gears are engaging correctly. It will be a bit stiff as the permanent magnet tries to hold the armature still but it will turn - push the wheels on the side with the gears not the other side. This is to avoid accidentally moving any of the wheels on the axles.

Finally instal the brushes and test again before soldering any wires back on.

Good luck, you'll get there.

No continuity between armature/collector poles could indicate broken winding wires. Is that between any poles?
The sparks in the first video indicate current flow. How much is that?
Any resistance between the brushes? Should be a few hundred Ohms.

Hi,

I found a 2nd hand replacement motor and it worked straight away. Loco now runs.

Maybe I’ll try to investigate a bit more what’s wrong with the broken one.

-Eino