Model Railroading > A Weird DCC Problem

I am working on a yellow box Atlas S2 that I picked up used. I am putting in a NCE ATL-S4 decoder.
I made sure that the motor was isolated from the frame and I installed the decoder. The engine programmed just fine on the programming track.

Here is the weird part. The unit runs fine forward. However it will not move at all when I switch to reverse. The breaker for the power district is not seeing a short on the tracks. I then programmed the head light to dim in reverse. The headlight does dim so I know that the decoder is seeing the direction command, but the engine will still not move in reverse.

Have any of you seen an issue like this before? If so, what did you have to do to fix it?

Bob Perkins
Cedar Rapids, IA

Check to see that you're speed table is not configured oddly. I had a unit go forward, then reverse, then forward, because somehow the voltage values for Lo-Mid-Hi did not make sense (Mid was higher than Hi). I'm guessing it was because I had programmed the speed values "on the main" and it probably missed a value during programming.

Might want to grab your old DC power pack and doubke check that your motor works in DC if you havent already.

Chris

After you verify that the motor runs OK both ways on DC, test the decoder on a decoder tester or in another locomotive. There are separate transistors for forward and reverse so it is possible for one direction to fail.

Barry Draper

When you test that motor, check the drive shaft to the trucks too. It may be catching on something and can't turn in the reverse direction.

I was going to return this to NCE for replacement. However I was informed that NCE has discontinued this decoder.
I took a good hard look at the decoder and I found the problem. A circuit trace near the edge of the decoder was damaged when they cut out the printed wiring board from the panel. I ran a jumper wire and everything works now.


Bob Perkins

That is good news, Bob. I am glad repairs were something you could do in house.

Nice of you to follow through with a post. This goes a long way in helping out the next guy with a problem.

Posted from Windows Phone OS 7