I have had my O scale trains in storage for a long time now, so I am going through them one by one to get them up and running again. You will see a few more of these threads in the next few days, so I hope you are not getting bored, Just sharing. I am in the process of trying to find space for an outside in a shed 8'x16' layout
I found out that my MTH 20-3078-1 UP gray 4-8-4 would not move under DCS and the smoke not working.
I took it apart and found out two things: the white 9V battery was reading 2.32V and the smoke motor had one wire which had came off.
So fixed the motor wires ( the other wire broke off the moment I touched it, the wires were badly soldered on)
I tried to revive the battery using my great planes charger/discharger. after a few tries it came up to 8.32 volts. I know it is old and will die soon again, but I did not have a replacement so I decided to just put it back and play with the train till I replace it. It is an easy few screws off and on to fix it. The battery now works fine but it does not have its original capacity..this is expected for over a 10 year old nicad.
This is the charger I used to revive it:
Here are some pix of work on the loco....This is a great running loco now and it smoke sooo much!...Thx for looking
The tender and the dredded white 9V batt 
Urghhhhhh...
I decided to add a speaker baffle as an experiment. this is a cap from dish washing liquid bottle
Looks like a good quality speaker, 16 Ohms
Fairly simple inside but again wires never cleaned up!
You see the smoke motor wire broken?
Smoke unit with elongated output for the dual stacks
This is a very new unit (old stock but has only 5 smph on the loco) and already burned wick?
One beer for who ever sees what's wrong with this picture below?????
The smoke motor and wires joined company again! Tie wrap a few wires to clean it up and prevent pinching
The smoke motor wires are exposed for a possible shorting. Note the elongated whole where the smoke unit mounting screw is, you must positioned it here for the plastic smoke output funnel to line up with the boiler dual stacks!!
I added a small piece of electrical tape for extra peace of mind.
Lubed and greased the gear box which has two ball bearings, nice!
This is the finished speaker enclosure, sure it sounds better, I tested it with and without!
I added a tire wrap and tape to prevent any future problems. Painted the cap with spray can.
this is the LOW smoke setting...wow!
the rear coupler wires exposed, I added a piece of electrical tape all around, not shown.
This is how I store my locos...note the arrow showing the loco's right side up so it can be stored the same way if space allows.
Lubed it and oiled it and added smoke fluid, ran it for a while and it ran great, put back in the box for the next victim to be operated on...It may be a Lionel Cab Forward 
