Mallet locking up

[ChrisS]

 All of a sudden. My mallet is locking up. Will just be steaming along fine, the randomly the drive just locks up.  Decoder, sounds, and lights continue, just no
Motion.  I have to remove it from the track and the she'll start again. 
Anyone have this before? I never remove my locos from the track so there's no way it has been damaged by hand.  Last lube was last year, maybe 5 hours of operation.  I have checked the rods, they don't appear to be binding. I have checked the plugs under the cab.  Tomorrow I'll remove and reseat the decoder

[Stevelewis]

Hi Chris

When you say  its'locking up'  do you mean that  the   loco just  stops with  the  sound  still  working  OR  when it  'locks up' are    the  driving  wheels  actually locking?

A way of finding out  is  when the  fault  occurs  cut the power and then  remove the loco from the  track, then carefully place it on its  side  and  gently try to move the  driving  wheels  VERY slightly,  they should  have  a  small amount  of 'play' in them,  If  either set  doesnt have any play  then it  could be  that  the valve  gear ( the  rods) may need checking.

I have  had 0n30 locos  which have done what  you  describe,  and the  fault  was  traced to the  valve  gear needing to be  correctly  re-positioned,  it is  always  worth  checking  that  the  retaining screw  on the  connecting  rod & valve  gear has not  become loose.

The fact  that  the  sound  continues to work  fine, indicates  that  the  decoder is  probaly not the  cause but  its  always worth cheking in the  tender to make  sure. Hope this  helps.