I am having a problem that is a first for me. I just installed an NCE decoder (N12A0) into an N scale Atlas U23B model. With the shell off, everything works fine. When I put the shell back on to the frame, I get no response from the locomotive. Take the shell back off and everything works again. What might be causing this?
So, you have no lights and no movement? How snug is the fit on the electrical contacts? I don't have a U23B, so I'm only guessing on things a bit, and you may well have already looked at these suggestions. Has the decoder shifted at all when you take the shell off? Does the system short when you have the shell on? Still thinking...... Jeff
No lights, no movement, nothing. In fact, when I tried to program the decoder with the shell on the frame, I got a response of "no decoder". But when I take the shell off, everything works perfectly. I programmed it with no problem, test ran it, it runs great. Put the shell back on and it goes completely dead. Everything seems snug, nothing seems loose.
Hmmmmm..... Well, when you put the shell on, the halves of the frame are going to get sqeezed together. If you've got an Ohmeter you might be able to probe the frame from below and make sure the halves are not touching, though it does not sound like they are. You might also put the squeeze on the frame and see if the contacts between the frame and the decoder get separated. Since you don't have lights it doesn't sound like the problem is a disconnect between the decoder and the motor. The "no decoder" message isn't really too helpful, since it only means that when you try to program the decoder the motor doesn't draw any current. The only way the control station can see the decoder is by detecting current drawn by the motor. So all that tells us is the motor isn't getting power. Since you don't get lights, that tells us the decoder isn't getting power. So I'd look really carefully at the contact from the frame to the decoder. One other thought, I took a quick look at the installation instructions yesterday, did you put on the kapton tape to make sure the motor contacts are isolated from the frame? Jeff EDIT: You didn't specifically say, does the coltroller show a short when you put the shell on, or just this loco does not do anything?
Sounds like the board is losing contact when the shell is replaced. Have you added a little solder to the four frame contacts on the decoder? NCE replacement decoders are thinner than the stock Atlas lightboard and can be problematic due to this. A small puddle of solder on each contact area or a .010" - .015" strip of styrene under one (or both) ends of the board, between the decoder and frame, generally fixes this. Also, make sure you have adjusted the motor contacts where they touch the board for moderate spring contact and proper alignment. Test the loco in program track mode to limit fault current, with the shell off and on, before testing on track under normal operation. Installing the Kapton tape as Jeff suggests is a good insurance.
Don't know, but the TCS AMD-1 is a snap-fit pulh&play substitute for the Atlas light board. It works wonderfully well with the shell on.
