MTH PS 2.0 Mikado Problems - tender smoking

The upright board in the tender is a multiplex board, MUX for short. If you replace the wire from the MUX to the 8 pin connector, I would turn off the smoke unit before firing it up, as that is one of the features the MUX controls. Something happened inside the loco, pinched wire or something shorted where the power and ground screws are connected to their wires. I suppose your loco has a Pittman motor, you could test it to see if it works, tho I would be surprised if anything was wrong with the motor. If my memory serves me correctly, the blue wire is hot from the board to features on the loco. Someone else, like GGG or Gunrunner John hopefully will chime in with more advice. 

The blue wire is PCB ground.  Most likely the PS-2 5V board died if this is the early PS-2 5V Version.  IF this is a newer 3V version, than as Luke stated you may have pinched a wire in the engine and that damaged the harness and possibly board.   Most likely you need a new harness too.   G

I took the shell back off the locomotive today and I found a pinched blue wire and a partially pinched purple wire.  Boy do I feel dumb!  Nothing looked melted on that end, so I am going to cut the pinched part of the wires off and solder them back together.  I am going to do the same in the tender and see if that fixes it.  I don't see any other damaged wiring besides these.  The MUX board looks fine and I can't see any visible damage to it where the harness plugs in or to the blue wire that comes from the main board to it.  I pray there is no more damage to it than these wires - or it'll be a while before I can dump the money on a PS3 upgrade.  Do any of y'all happen to know the part number for the tender wiring harness just in case I need to replace it?  I checked the MTH website for a part list for this locomotive and was not able to find one for it.  Thank you so much for your help.  I truly appreciate it.  I know now to be more careful putting the shell back on!

Thanks,

Caleb

if I remember correctly the part number for tender is BC-1000005 and the loco harness is part number BC-000003 the last time I tried to order they were out of stock from mth!

good luck!

Alan I think they are $15.00 each plus shipping

here is the web sight! mthtrains.com

http://mthtrains.com/parts-search/BC-1000005%20

http://mthtrains.com/parts-search/BC-1000003

Those are 3V part numbers for generic upgrade kit harness, except BC-0000003 is not.  We would need the specific model number of your engine, and most likely that harness would not be available.  You need to custom wire that tender blue wire and you might need the generic external tether and wire it up.   The current that burned the external blue wire in your tender most likely heated and damaged internal wires inside the tether.  A continuity test of all 10 pins is required, or just replace it.  Unfortunately, there is a high likely hood your board is damaged too.  The blue is DC Ground and if it was crushed to the chassis AC ground that can kill the boards.   G

I finally had time to work on this today.  I replaced the fried ground wire in the tender coming from the tether, put it all back together, and it started working again!  Thanks for all your help!