MTH J Imp won't move.

I had these screws backing out of my Allegheny Imperial but it typically only happened at low speed and I caught it quickly (luck on my behalf - nothing else).  The eccentric rod would wedge up into a gap in the boiler and the drive wheels wouldn't budge.  Normally they don't turn, but have a little play.  When they were wedged, it was tight with no movement.  I was able to carefully dislodge the rod get that returned the slight play in the driver.  It would work until the screw backed out again - turns out that blue loctite is your friend  in some cases

To your situation, I asked my LHS MTH tech what would happen if either:

a)  It happened at hight speed (you can bend rods)

b)  I didn't catch it for a while (motor burns out/gears are damaged)

I'd take it to LHS at this point, but there may be others with better suggestions.  Good luck!!!

-Eric

Eric:   Spontaneous disassembly happened at 15 smph. I just removed the shell. Turning the motor drive shaft by hand easily turns the wheels. All the wires and connectors seem intact. All the rods have slack in them. 

So I am down to a dead motor, or a problem from handling, i. e. turning upside down, laying on its side, ... 

Anyone know how I can test the motor or further identify the problem?

Could it be inside the tender which I have not opened?

If your loco has the board set in the loco, unplug the connector on the rear (two wires) that have a yellow and white wire pair going from the board to the motor. Take a DC transformer, set at about 8 volts, and apply DC current to the motor at the white and yellow. You will either get the motor to run or the circuit breaker on the powerpack will trip. Motors are availalbe from MTH and are not frighteningly expensive. While there, see if the motor is free by turning the flywheel, which also makes sure nothing in the gearbox was damaged. I don't know where you are located, but if I can be of any help, don't hesitate to ask. Email in profile.

If you turned the drive shaft (or use Flywheel as Train Doctor suggested) and the wheels turn freely then you reassembled it correctly and the motor should have no problem turning the wheels.

I always turn the flywheel sufficiently to get a few rotations of the wheel in both directions to ensure nothing binds at a specific spot.

The motor test TD stated is the next step.  If the motor runs fine, there is a possibility the current surge when the motor stopped damaged the board.  I would hope it is the motor, since that would be a less expensive replacement.   G

 Motor was free and runs smoothly without extraneous noises. 

Manually turned flywheel for a few rotations of the drive wheels. All was well.

Reassembled. Checked many things with DCS remote. All seems proper except that loco does not move or try to move.  Can I get whatever part I might need from MTH or preferably from a dealer? What would I ask for? It looks like the controlling part is the small circuit board mounted in the top of the shell.

I am in Farmington Hills, Michigan. It would be nice if posters locations were show under their name like other forums I visit.

Does this J have the PS2 board in the engine?  If so disconnecting the motor lead from the board and using solid core wire you can push into the connector that came out of the board, one to white and one to yellow and power the motor via a battery or DC transformer.  If it runs the harness and leads are fine, and some component on the board may have gone bad.

If you have a tech with a board testor he can verify the board works or that it doesn't drive the test motor.

If the PS-2 fires up and drives smoke, lights and sound, and the motor doesn't work, I think you may have damaged a component on the board for driving the motor.  G

Next step would be to test continuity from motor connections to yellow and white wires at the board, with the tender tether plugged in. If no, check from tender tether to connector at board, if OK resolder the tether board where the pins are accesible on top of the tether board, making sure to get the ones that are connected to the white and yellow wire. If this doesn't work, make sure the continuity is from motor to the tether board in loco. Has to be an open somewhere. Keep us posted.

After reviewing the last two posts numerous continuity tests indicates a problem:

The metal contacts in the tether plug all reach to the end of the shell except for pin #1 which is white from the motor. Its contact is recessed 1/16" or sightly more. If the tether is plugged not quite all the way into the loco and rotated a bit there is power supply to motor continuity. 

It looks like a new tether is needed. I try to forget and forgive my previous experience in getting a part from MTH. Could I get this part from a dealer? It would give me an excuse to make a 50+ mile trip and see some nice things.

Grab the recessed pin and pull it out with a pair of needle-nose pliers, see if it works.

The MTH tethers are known for failing over time. The wires are very small gauge and don't hold up that well to constant twisting & bending motions. A friend of mine has had several replaced on his MTH locomotives. If it turns out to be the tether, contact Chuck Sartor at Mizell Trains & Hobbies 303-429-4811 (Denver, CO area). He usually has them in stock and they're reasonably priced.  

An idea while shaving: Insert a clothes straight pin as far as it will go into pin hole in tether. Cut off that portion. Insert this piece with point outward and press into place until it does not protrude from tether.

Assemble everything. Disassemble everything. Remake connections I removed for testing. ***... & dis... tender to retrieve screw that fell in and is magnetized to the speaker.

Reassemble. Long run over most twisty route. Headlight is off most of time. Blinks occasionally and when bouncing over switches. Something is loose. Story of my life.

Thanks to all of you. If it does not hold up I will call Mizel Trains for a new tether.

Well, you have the failing part identified, so I'd probably just go ahead and get a new one.  I don't put up with stuff like lights blinking, etc.

I changed out the tether on my friend's MTH "J" the last time it acted up. On his engine the tender back-up light became intermittant and the rear coupler wouldn't fire. That was enough to convince him that it was time to replace the tether.