DCC fitting confusion - Farish Class 04 N scale

  Gremlin Assistant Commissioner

Hi All

This one has me very confused.  I have a Farish Class 04 diesel, Chinese-made Bachmann/Farish, which has run satisfactorily for some time.  I am trying to hard-wire a DCC chip and have followed http://yourmodelrailway.net/view_topic.php?id=4935&forum_id=10 which is a simple guide for a simple loco.

However, placing it on a program track immediately shorts out the NCE ProCab.  Checked the very few connections, all good.  Checked the decoder in a tester, no problems.  Just for fun, put a multimeter continuity tester across wheels on both sides and... short.  Removed the decoder and tried again, same result?  Tried continuity test on another non-DCC loco and... same result.

I haven't had this problem before with any loco and I'm struggling to understand how it can be both short circuit across the wheels yet run OK on DC?  And I'm not even certain if this is the problem.  Putting the wires back to normal and placing it on a DC track and it runs fine.

Confused... any help would be appreciated.

On the suggestion of Jarryd Langford, removed the capacitors and tried again - still a dead short.  Completely removed motor from chassis and placed multimeter across motor power tabs - dead short!  Placed motor back in chassis and connected wires and placed on DC track and it runs happily...

[EDIT 2]
Got it!!! Completely disassembled absolutely everything and found that one of the pickups was, from the factory, completely bent under and touching the bottom conductor plate! How it ever ran is a mystery. Anyway, bent it back to perpendicular and refitted and - everything works and no dead short!

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  dthead Site Admin

Location: Melbourne, Australia
good work there and always useful to tell the entire story, which may help many. often people have a problem, and we never know what the results were, so it was well worth posting.

David Head
  Gremlin Assistant Commissioner

The motor, out of the chassis, was reporting a dead short when using a continuity tester; when using the multimeter on low ohms, it actually read about 40 ohms, so not shorting.  This checking method was suggested by Gary Windsor on Facebook.
  Captainchoochoo61 Locomotive Fireman

alls well that ends well.

And I agree, it is great that you came back with the final result so we can all learn something.

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