DCC mixed equipment question

I have the same problem with a Spectrum Lt Mountain equipped with a Soundtrax decoder. When I contacted Soundtrax they told me to reprogram the decoder to the default setting and then reprogram it to my specifications. That seemed to work for a while but the problem has resurfaced and the loco again takes off periocically on it's own. Fortunately, since that loco spends most of it's time in the Roundhouse, I don't have to look far to find it.... down in the Turntable pit.

For now my practical, if inellegant, solution is to stick a pushpin between the ties directly in front of the locomotive. Crude, but effective.

I'll be anxious to see if other readers can solve your (our) problem.

Carter Braxton

Prototype RRs generally parked their locos head first in the round house. Steam engines have been known to creep, and it's a lot easier to fosh a tender out of the pit than a 2-8-2.

Perhaps adding a DPST switch to make that loco's stall dead until you want it would help.

Make sure you have the DC mode turned OFF, if the locomotive thinks it's on DC and sees 18 volts off it goes Wheeee!!!.

-Hudson

I always thought the reason was so that there was more access room around the cylinders anv valve gear, an area that often needed adjustment.

thanks for the reply. I will try disabling the DC mode. I question though how the decoder thinks it is on DC anyway? And the problem occurred with two separate decoders!

Bruce

It's possible that the decoder lost communication with the command station/throttle and went bananas. It's like a computer - if there's a glitch in the data stream things can go bonkers.

Hudson has it right. One should *always* disable DC analog mode in all decoders until one wants to actually run it on analog DC. If you want

4-digit mode, forward direction, 28/128 speed steps, and analog mode off, one must program CV29=34. If you want the same thing in 2-digits, CV29=02. I have seen all makes and models of DCC decoders (Digitrax, Soundtraxx, Lenz, NCE, etc.) go flying down the track if DC analog mode is left on. Some decoders are more vulernable to this than others. As for the reason, it was explained to me thusly: When one has a short circuit (or other kind of power interruption), the voltage in the track "crashes" to zero. When the power comes back on, the first initial burst of power can fool a decoder into thinking it's seeing a straight DC voltage. When analog mode is turned on, the decoder will (under DC mode) put the available voltage in the track and throw it to the motor. And since DCC is always on at full voltage...away you go! Also, I've been told to do a memory dump of the system on a regular basis to keep "ghosts" from clogging up the system.

Paul A. Cutler III - Digitrax user since 1999

************* Weather Or No Go New Haven *************

If it loses communication, it won't go bananas, it just will continue doing what it was last told to do, or stop entirely (depending on the situation). If it gets "noise" from the system, it may go bananas...but that's more of a "too much info" situation...in a manner of speaking. In my experience, they tend to lose the connection from the throttle to the decoder much more often than going bananas.

Paul A. Cutler III

************* Weather Or No Go New Haven *************

The old Soundtraxx decoders had some kind of timing issue with Digitrax systems. Each blamed the other (I asked each of them at the Springfield show a few years back). The Soundtraxx sound & motion decoders would go into the "Soundtraxx Shuffle" (as we called it) for no apparent reason. When running normally, they would suddenly change direction for a split second, then go back to forward again. This was odd looking to say the least. Oddly enough, I've never seen this with any other decoder, and the newer Tsunami decoders from Soundtraxx don't have this problem.

Paul A. Cutler III

************* Weather Or No Go New Haven *************