it's very hard to help you or anyone else without having an engine item number? do you tell the doctor you don't feel good and what's wrong without giving any information ! we need the symptom's and exactly what engine you have ps2 3 volt, ps2 5 volt ps 3 ???
then we can help you, I'm assuming you have a older triplex and if so is uses a 8.4 volt 8.4 volt battery and if it's uses the 5 volt boards and they can fail at any time. you might have engine item number 20-3069-1 !
L:\_Library 1 - Instruction Manuals\Premier\Steam\20ST14482I_Triplex\20ST14482I.PDF (mthtrains.com)
Alan