Picked up a Lionel MPC era (I think) N&W SD24 a while back.
It shorts out on any of my 031 O guage tubular curves if the rubber tired wheels are on the outside of the curve. It runs fine if the rubber wheels are on the inside, and on all straight track.
I’m at a loss for what to investigate. Perhaps someone can give me a clue?
runtime
It has nothing to do with the traction tires, just left turns. You’ll have to pull the cab off & check for wires shorting out when the trucks pivot(both the power truck & trailing truck). Keep in mind that the cab might be deflecting the wires when it’s on, so inspect carefully.
I have seen on MPC era diesels one of the field wires with extra slack contacting ground as the power truck pivots(the enamel having rubbed off). This is particularly puzzling because the motor stalls, but there is not a dead short.
Rob
Thanks Rob,
I pulled the cover and found an electronic circuit board resting loosly on a crumbling foam pad and deterioratiog strip of plastic tape.
The board is not secured in any way, so when it shifts, the prongs on the bottom can contact the metal frame. With the board carefully positioned, the engine seems to run fine.
So I think I just need to devise a way to secure the circuit board (loop an insulated wire tie through a slot in the frame and aroung the board?), and perhaps insert some type of cardboard, plastic or foam between the board and the frame.
Seems like an odd way for Lionel to have built this. Was the tape originally stuck to the board and the foam? The foam seems glued to the frame. Or is this some sort of later modification? I only run conventional, so have no idea what the electronics do.
Comments and suggestions appreciated.
runtime
The double sided tape has dried out, not all that uncommon. Get your self some new double sided tape to replace the old . Then you will be good to go. The tape acts as the insulator and a mount, so replace it before the board shorts out.
Thanks; that sounds much simpler than what I was contemplating. So the foam is irrelevant and doesn’t need to be replaced?
runtime
The foam was proballly just thick doublesided tape that has degraded leaving what looked like tape holding the foam. Any good quality double sided tape that is thick and has good adheasive will do. You want it thick so the little soder nubs on the back of the board stay away from the frame.
Got it. Thanks again
You should use double sided foam tape, not just double sided tape.
Try using a piece of cardboard as the insulator. This is the same problem as found in the sounds of steam tenders.
Double-sided tape isn’t know for outstanding adhesive qualities. Heat has a negative effect on it. I suggest you use a better adhesive like RTV silicone cement, unless you want to be repairing it again in the future.
YES, this is the proper repair method. Found mine in blister packs in the office supply section - rectangular shaped. I just cut two strips to mount the board to the chassis.
Rob
Hmm…It’s getting more interesting. Well I didn’t see the last few posts before I went to Home Depot and got some double sided tape intended for mounting things to walls etc. I guess it’s foam cored. I can see that there may be a future problem, since the sticky tape only makes intermitent contact with the underside of the circuit board, due to the electrical connection points sticking out as they do. But I guess it will last for a while. Since the Engine doesn’t do very well pulling 20 cars (front trucks derailing, rubber tires out of allignment), it may get parked anyway, at least until I find it a twin.
runtime
Have you tried adding a little extra weight in the area adjacent to the front truck ?
Is this a single or dual motor loco ? Found this which answered my question.
www.lionel.com/customerservice/service-documents/download.cfm?file=70-8152-250.pdf
For maybe an added comfort zone you could double up the foam tape