Had my first runaway last night, so I thought I'd pass the info along. System is Digitrax Empire Builder, decoder is SoundTrax DSD-100LC for Diesels. I was running some trains (HO, by the way) for the first time in several days. The diesel loco seems to be sensitive to dirty track. It's also programmed for manual engine sound control, and set so that the loco won't move until the engine sound is started. Anyway, it stopped several times at the same location, so I decided to take a few minutes and clean the track. Details: Once the loco stops for a moment, even if it regains power, it won't move until the engineer manually restarts the engine sound. I had a UT-1 throttle set up for this loco. Since it was stopped, I just laid the throttle down, but left the throttle knob at the last speed selection. Left another loco running on another line, controlled by a DT-200 throttle. I guess I must have spent 10 minutes or so cleaning and troubleshooting. Suspect the Digitrax system purged the diesel loco since it appeared to sit unused for so long. Anyway, I think I must have momentarily shorted something, because the running loco stopped, then both restarted! Diesel loco would not respond to the UT throttle. I "captured it" with the DT-200 easily enough. My theory is that even though the diesel loco was not running (due to the sound-power software interlock), the system had a speed command in the decoder, even after the loco's address was purged. The power glitch must have somehow aroused that loco. Any ideas or comments?
That's happened to me before, a few times. I've had all my trains start running at the same time (full speed!) when I shorted out the track. Always wondered if there was a way to avoid this happening (besides never shorting out the track while engines are running!). Great question Warner!
Pete, What decoders do you use? While not pertinant to the original posters question, if you have all DH121 or DH120 the problem may be the decoders. I also had problems with trains taking off for no apparent reason. I quickly figured out it was after restoring track power after a short. Not all locos, and not every time. Locos with DH140 or DH142 had no problem, nor did my one NCE decoder. I noticed it was only DH121 and DH120. With all other locos off layout, i would short the rails repeatedly with just one DH121 equipped loco on the layout. It might take 5 or 6 tries, but eventually it would take off. some DH121 did not do it. This was two years ago. Evidently Digitrax figured out the decoders had a problem, as after several conversations with John, he told me to read one of the CV's (don't remember which one) which was basically a lot code. All #'s below 17 (I think it was) were suspect and they exchanged all of them (12) for me at no charge. You might want to check this. For the problem with the soundtrax, I can't say for sure but I also had a problem with a UT throttle losing control of a loco when the system shut down for a short. When track power was restored, the loco I had been running started at the speed it had been at, but I could not control it. I had to grab it to keep it from going thru a turnout thrown against it. When i tried to acquire it with another throttle I got the message that it was already selected. I had to "steal" it to get it back, even after letting everything sit overnight. It happened with people over to operate of course. This has happened several times, only with the UT throttle, which may require a trip to Georgia. Gary
The UT series are a line of simple (inexpensive by DCC standards) by Digitrax. I bought one to have a second throttle for "guest operators." See http://www.digitrax.com/ut12.htm
There has been / still is some discussion on the Yahoo NCE board about this (or a very similar) problem with a number of makes of decoder, including Soundtraxx. A suggested cause is the 'DC mode' - apparently on repowering after a short the decoder can believe it is on DC and of course g-o-o-e-e-e-e-s-s-s. The way to test this is fairly obvious .
I agree, this has been discussed on the NCE board. Some people may have programmed their decoder to run on DC as well as DCC. When the short happens the decoder momentarily goes to DC until DCC signal is required. Since DCC is always on full track power, the locomotive will take off until DCC comes back and tells it not to. Therefore, if you can program decoder to run DCC only.
Thanks for the comments, gang. Have to admit I wasn't aware of the NCE board postings. I think I could spend all of my modeling time just checking various bulletin boards! Back to the original post. Two other locomotives, SoundTrax equipped, did not move. The "Runaway" was moving rather slowly, nowhere near full speed. For those considering DCC, don't let this thread scare you. This has happened to me once in a year of DCC operations. Back in my DC block days, I'd inadvertently enter a powered block all the time, often with quite entertaining results.
Robin, I consider the UT throttle to be the "Throttle for Dummies." I have one and it is a great throttle for yard work and the like. The reason many non-dcc types like it is that its very basic. It looks like other throttles used on non-dcc layouts - big knob, reversing switch, emergency brake, directions, etc. It doesn't have all the programming lingo on the other throttles. Its the perfect throttle to hand new guest to the layout and to dcc. Unfortunately it doesn't come infra-red equiped or radio ready.
It's been a year since my locos "took off running", so I don't remember which ones they were, but I believe what happened was, power to the track was interrupted, and when it was restored the trains took off. It's been so long, I can't remember if it was all the locos on the track, or just the ones that were moving at the time the power was interrupted. When I say "power interrupted" I mean, once I shorted out the track, once I turned off the electricty to the power supply, and another time, the voltage just seemed to drop. On the DT300 throttle it tells you how much voltage it's getting, and one time the trains just stopped. I looked at the throttle and it read a much lower voltage. When the proper voltage was restored the trains took off running. In each case, as soon as the the power was restored, the trains took off. The problem was not partial to decoders, as I have a mix of Lenz, Soundtrax, and Digitrax decoders.
Jackson, I still suspect the UT throttle. Try an experiment. Run a loco at slow speed with the UT, intentionally create a short, the restore track power. See if the loco resumes running at same speed as before short, and whether or not you still can control it with the UT. Everytime there is a short while I am running a loco with my UT, I lose control of it. Doesn't seem to matter what loco, and this doesn't happen with any other throttle. I do need to check my wiring because when I get a short (for instance someone tries to run thru a turnout thrown against them) the breaker on my TTX power supply trips rather than the DCS100 just interupting power. So perhaps if the DCS100 cut power without the breaker tripping, I wouldn't lose control. I'll check it someday! Gary
