The Murphy's Law DCC Install

A guy I recently saw on a reality TV show said, "All lessons cost money. The best ones cost a lot." The most troublesome DCC installs I've run into are for the earlier Atlas S-2 and S-4 locos, inclusing the Atlas-Roco yellowbox and the later Atlas-China ones that use the older Roco design. I haven't tried any of the new Atlas versions, which apparently have sockets for decoders. In fact, I've held off getting any new Alco switchers, Bachmann or Atlas, until I get a lot of my older Atlas ones converted.

These were really good locos in a DC environment. They had good weight for switchers and were very smooth runners. The paint was a real step forward in the Atlas yellowbox era. The trouble is that they were never envisioned for DCC conversion. The motor isn't isolated from the chassis, and in fact, it's held on by a metal screw. Beyond that, the motor brush contacts aren't isolated, with the current fed directly through a weight over the motor. This gives several major points of failure in an install, and according to Murphy's Law, anything that can go wrong, will.

At one point, both TCS (the AS6) and NCE (the ATLS4) made theoretically drop-in decoders for these older Atlas Alco switchers, but they discontinued them very quickly. I think it was because so many things could go wrong in an install and smoke the decoder that they were getting too many "no worries" or "goof-proof" warranty claims to make money on the product.

Poor instructions were probably part of the problem. For whatever reason, I had two installs, both NCE and TCS, go well at first, which made me overconfident, and I then promptly smoked two others. By then, both NCE and TCS had discontinued the products, and I couldn't get an easy (or easier) replacement.

Here is what I learned you absolutely must do:

• Remove the motor, but first be absolutely sure which is the top side. If you do not do this, and you install the motor back in upside-down, you will smoke the decoder.
• Insulate the bottom of the motor with tape so none of it can come into contact with the chassis. If you don't do this, you will smoke the decoder.
• Poke a hole in the tape at the location of the motor mount screw. Replace the metal motor mount screw with a plastic one. If you don't do this, you will smoke the decoder.
• When you replace the motor, be sure not to lose the universal shafts. This is a pain in the neck, but at least it doesn't smoke the decoder.
• Isolate the weight that goes over the motor from the chassis with Kapton tape at four points. If you don't do this, or if you don't get it 100% right, you will smoke the decoder.

If you followed all these steps, the old TCS and NCE Atlas Alco switcher decoders could go in and work. But now that these are no longer available, you have to revert to older procedures for a hard-wire. This is a good one, but you have to be sure you make all the cuts on the old PC board correctly. If you don't do this, you will smoke the decoder.

There's one more gotcha: there's very little clearance between the shell and the chassis-motor assembly. If you aren't careful, you can damage the decoder when wires get caught between the motor and the shell. Ask me how I know.