I have HO scale E-Z 'CARGO KING' set with EMD GP40 Diesel locomotive. It was rare used when my children played with this set. Most of the time it sits in the box. Something happened last time when children played with the set and now locomotive does not power up. There are no lights on locomotive and no engine live. I have checked with multimeter the rails and they show Vac value. I put the locomotive only on one piece of the rail which has a power but locomotive looks powered off completely. I am not sure what wrong is. Is it power supply problem or locomotive issue? Can somebody help with the advice, please? Thanks!