SW1200 problem

[Fish]

From what I've read the poor design on the brass contacts on Walthers SW1200 switcher and the easy potential for breakage of the contacts when removing the shell to access the motor, is common. I ordered a new walkway with intact contacts from Walthers.  I also installed a Digitrax decoder since the model I had was Dcc ready. The decoder went in fine.  The problem I am having is the failure to get a stable electrical connection again.  When I put the walkway with contacts on the un-shelled  body I get a connection and the engine runs.  However once I connect the walkway to the shell and place on the body, there is nothing.  Remove the shell, connection restored.  Put back the plastic shell and nothing. My feeling is that somehow the shell (with new contacts) is shorting, but how or why since it is mainly plastic.  Can any one offer some help?

[James in FL]

I am somewhat surprised that Bachmann has tolerated this post this long.
At the risk of getting both our posts deleted...
Sounds to me like you have an "open" rather than a "short",
When you put the shell on you are forcing something apart rather than together.
If it was truly "shorting" it would have negative effect on your system, probably shutting it down for a time.
Check continuity.

There are other N scale specific forums that are much more tolerant of discussion of all manufactures N Scale products, both good and bad.

[the Bach-man]

Dear James,
No one's being negative here.
If someone can help, let's do so!
Have fun!
the Bach-man

[spookshow]

I agree with James, I don't think the shell would cause a short-circuit in and of itself (it being entirely plastic), but putting it on may be causing problems with the motor wires. How snug is the decoder installation? I could see the shell pushing down on the motor wires and maybe causing the decoder to move around and lose contact with the chassis if it's not tightly engaged in the chassis slots. Or maybe the shell is causing one or more of the wires to lose contact with the decoder. Are they soldered to the decoder or just pressed into it?



-Mark

[Fish]

Thanks for the helpful comments and you have given me a new perspective on the problem.  The board appears to be in tightly and the wires have been checked and are in securely.  I was concerned that the shell, which I know is plastic, though the cab does have metal weights inserted for improved traction, might be pushing the board down and making contact with the metal body.  Coincidence or otherwise, not having kapcan tape, I added a piece of black electrical tape under the front of the board, put the shell on and have been able to get a steady running engine.  Though not nearly good since it runs but at a slower speed than expected when compared with other switcher type diesels.  The tape may have be keeping other things from moving.  Thanks again for your input.

PS - I had no intention of violating any blog protocols and I appreciate Bachmann's comment.