runaway

[SteamGene]

I was cleaning ttrack with one loco as motive power for the cleaning car when a second loco took off.  It was not on my throttle and the only thing that kept it from crashing into another loco was the fact that it ran a turnout at about 50 MPH and the front engine derailed.  I went ahead and punched its number into the throttle and it went back to where it had been. 
Any idea as to what might have been the cause?
The loco I was using is an older BLI and the runaway is a Spectrum with either an MDC or a Tsunami powered by Digittraxx. 
Gene

[Tim]

Gene

I have seen this happen on my layout with older BLI/QSI loco's, and
also when running on dirty track.

The older QSI decoders cause signal noise which can effect other decoders.

The other decoder thinks it's being told to do something, in your case go forward.

Two solutions for this problem.

1: Make sure the effected decoder is set for digital only, not dual mode.

2: Install a noise filter at the end of your power buss.

The noise filter consists of a .01 ceramic capacitor in series with a 100 ohm 1w resistor
connected across the buss at the end of the run.

Tim L. Anders
Souderton, PA

[Jim Banner]

Gene, another possibility is that your runaway was never released (dispatched) from your command station at the end of an earlier session.  It may still be associated with a throttle in one of your command station's slots, even though that throttle is no longer connected to the layout.  Easiest cure in this case is to clear all decoder information out of your command station by closing option switch 36.

[SteamGene]

Thanks for both responses. 
Obviously, I'm still cleaning track, though the runaway was on fairly clean track.  Also, I'd been running the BLI for a good ten miinutes, maybe longer before it happened.
I try to dispatch each loco at the end of a session - though I'll admit I sometimes forget. 
All the power busses just end; however the two locos were in different power districts and were separated by a fair amount of track. 
Since the first posting, it happened again, same two locos, but this time in the same power district. 
I wish Digitrax had some sort of a signal to verify that the loco has been dropped.
Jim, I'm not sure I'm clear on "option switch 36."
Gene

[Running Bear]

Some dual-mode decoders have a nasty habit of jumping into DC mode when there's a momentary short or spurious noise. To eliminate this change the decoders dual-mode setting from Analog Conversion to DCC Only.

[SteamGene]

That sounds like a good idea.  My layout is DCC only - except for the hidden test track.
Thanks.
Gene

[Yampa Bob]

I had a somewhat similar experience.  While running one from the yard, an adjacent loco started moving slowly.  I hit the button for the creeper, apparently I didn't closed its throttle completely when parking it. It's odd though, as I had previously turned off my master switch, I thought that "dispatched" all locos. 

The two locos both have Bachmann decoders, might have just been noise.

[Jim Banner]

Setting options switches (or OP switches) is covered in your manual, near the end.  Depending on whether you have a DSC100, DB150 or a DSC50, the exact sequence of push buttons changes.

For the Zephyr/DSC50, see page 46 in your manual or go to the link below and scroll down to page 46:
http://www.digitrax.com/ftp/zephyrmanual.pdf

For the Super Empire Builder/DB150, see page 107 in your manual or go the link below and scroll down to page 107:
http://www.digitrax.com/ftp/superempire.pdf

For the Super Chief/DSC100/DSC200, see page 115 in your manual or go to the link below and scroll down to page 115.
http://www.digitrax.com/ftp/superchief.pdf

By setting OP switch 36 to "c" (closed) you clear all the decoder information out of your command station.  You do not have to set OP switch 36 back to "t" (thrown) because the command station will do this automatically for you.

Your command station will also automatically "purge" locomotives if they have not been used for a certain length of time.  But this purging will not occur if you have it shut off or if the locomotive speed is non-zero (some exceptions apply.)