Need help with troublesome engine

[DWS3]

Sumner,

Yes, I think we are saying the same thing. My multimeter does read resistance but has a continuity setting that makes a constant tone if electricity is flowing. Putting the multimeter leads on each engine tab creates the sound, showing that there is an electrical path through the motor. When I put the multimeter leads on the motor tabs (or other part of the motor) and any part of the engine frame, I do not get a sound. This shows that the motor and frame are electrically isolated from each other.

D.W.

[peteski]

What Sumner was mentioning is to  measure actual  resistance of the motor.  Does the continuity setting also show resistance on the display?  If not, put the meter on its lowest resistance  (Ohm) range and measure the motor's internal  resistance. the reading will likely keep changing, but should be in the range Sumner mentioned.  If it was a "dead short" (close to zero  Ohms) then that would be a problem.  Continuity is just a go/no-go type of a test. Sometimes there is a need for a more precise measurement.

[DWS3]

Ah, gotcha. OK I measured using the ohm meter and got about 140-200 ohms (.140-.200 kOhms). Does that indicated a problem with the motor? It is a 25+ year old motor.

Thanks!

D.W.

[peteski]

200 ohms seems a bit high for a motor like that but since it's been sitting for some time the commutator is probably gunked up or oxidized a bit, creating the extra resistance.  You also mentioned that you ran this model on DC and it worked ok.  As long as the resistance is not too low (close to zero, or very high like thousands of Ohms), then the motor seems ok.

[DWS3]

Hey everyone,

Just in case, anyone comes across this thread in a search, I wanted to post the final ending.

I received a new M1 decoder from TCS under warranty, as the first one was shorted out. Still not sure how that could have happened but apparently it did. In any case, the new decoder, keep alive, and LED lights are installed and after about 20-30 minutes of running, everything seems to be working! Now I am starting to make adjustments to BEMF, speed tables, etc to get it to run the way I like. Ironically, it actually seems to run a little better without BEMF, especially at lower speeds. I am assuming that is because the keep alive helps on any dirty track spots but I do need to clean the track a bit since it's been sitting for a couple weeks.

I have not yet sent the ESU decoder back for testing but suspect that whatever shorted the TCS decoder also took out the ESU decoder.

Thanks again to everyone for all the assistance.

D.W.