Mainline Short Causes AR-1 to Start Clicking

Model Railroader Electronics and DCC
1

I have a pair of Digitrax AR-1 units on a lift out section, one AR-1 for each of two tracks. In other words, each track on the lift out section is its own reversing section. Each reversing section (a straight run of track) is gapped at each end and completely isolated from the double mainline that runs around the layout. The two AR-1s get power from the main bus and all of the feeders inside of each reversing section are connected to the output side of its respective AR-1 (or at least I think they are). It has worked flawlessly since I set it all up two years ago.

Last night, I had a derailment on the mainline very near to the turnout that leads onto the lift out section with the reversing sections on it. Althought the wheels of the derailed loco were not touching any part of the track in the reversing section, both AR-1s started clicking repeatedly. So, I did the quarter test on the mainline and, again, the two AR-1s started clicking. As far as I am aware, that should not happen. If the reversing sections are isolated and no feeders are connected to the main bus, a short on the mainline should not set off the AR-1. Correct?

This morning, I decided to investigate further. I started to purposely create shorts up and down the mainline, both near and far from the reversing section. It seemed that the farther away that I got from the reversing section, the lesser likely was the AR-1 to click.

So, that is a mystery to me. Should that be occurring? If not, what could be wrong?

Rich

2

Run a strong magnet along your track on both sides of the liftout, and through the liftout section, with the layout turned off. It’s possible that a small sliver of metal came off the locomotive or from some other source, and is shorting the track.

3

If the AR-1’s are powered from that main, and they happen to be in the position where they have the relay pulled in, and you interrupt the input power to them - they will click. You are removing and then reapplying power tot he AR-1s by shorting the main that feeds power to them. Whent he main is shorted, you should also see no power in those reversing sections, the way it’s wired.

–Randy

4

I did that and nothing turned up. The gaps are all adequate and no feeders inside the reversing section are wired to the main bus, just to the output side of the AR-1.

Rich

5

Thanks, Randy, for that explanation.

I went down and put a test lamp on the reversing section. While the lamp was lit, I shorted the mainline, and power was momentarily lost on the reversing section, as you predicted. So, that puts my mind at rest.

Rich