Atlas Nscale SD60 Short Circuit Problem

[Herc Driver]

Hi Guys,

I have two Atlas Nscale SD60 units, both are "Decoder Ready" as listed on their box. I bought two new Digitrax DN163A1 decoders that are listed as the correct choice - according to Digitrax.

I installed a Digitrax DN163A1 decoder in an Atlas Nscale SD60 and things didn't go well. The installation was straight forward, good electrical contacts made, and the decoder programmed on the programming track.

The fun started when I placed it on the layout. Nothing. No motor control, no lights. I double checked the engine connections, made sure the decoder was seated correctly between the frame halves, but still nothing. No movement, no light control, nothing except a quick rear light flash when the engine was first placed on the rails.

So I removed the dcc board and reinstalled the dc board...thinking it might be a bad board. When I placed the engine back on the tracks with address 00, the engine burst to life and surged forward and abruptly stopped, then surged again, then stopped. All the while, my Digitrax Zephyr controller was showing a short circuit indication. When I deselected the "Power" button to remove power from the rails (I thought), the engine surged forward at a high speed and without any control from the Zephyr. I lifted it off the rails. Since I've never seen this problem before, I repeated the procedure to see if it would do it again, and it did exactly the same thing. I tried the other Atlas SD60 unit (with its dc board still installed from the factory) and it did exactly the same thing.

I next tried to determine whether the Zephyr was bad, or there's something with these engines. I removed the strange acting SD60 engine, and placed a decoder equipped engine back on the rails, and it worked fine. No problems, no shorts. I chose another Atlas dc engine (no dcc circuit board installed - just the standard factory dc board), one that I bought about five years ago, and it worked in the basic dc mode on address "00" without any problems.

I checked the track, there are no pieces of metal "shorting" the rails. I removed all the other engines from the rails and tested only the SD60 unit, and it still had the same crazy problem. I don't have any other throttles hooked in the "jump" port of the Zephyr, just the basic unit by itself is supplying power and running the dcc operation. There's absolutely no problems running any other dcc equipped engine, or mixture of dc and dcc engines.

My only guess is there's something with these SD60 units. They were bought in different stores, in different states, but both have "1998" stamped into the frame. It is a split frame, with plastic inserts dividing the frame at each end where the frame screw is inserted to the nut. The motor's electrical leads touch the dc and dcc board at the correct spot.

I suppose there could be a problem with the Zephyr dealing with these particular units, but find that hard to believe. I had been running the unit for about 30 minutes without any problems just prior to this decoder install. And it runs other dc-only engines without problems.

Anyone have clue what's going on here? I'm stumped. I've tried to place the problem engine back on the rails this morning, and it did exactly the same thing as last night when I first encountered the problem. I don't know what's going on, but my guess is there's something short between the frames that I haven't discovered yet...though...I'm still in the "learning mode" of dcc theory and operation, so maybe there's a bigger problem here with the Zephyr that I don't understand.

Thanks for the help guys!