New Dreyfus Hudson J3 runaway

[tscroz]

I have a brand new Bachmann Dreyfus Hudson loco with TSC sound decoder i got from Trainz and when i put it on my track it immediately starts to run. I cannot control it with my NCE PowerCab. I can use the Horn Whistle and Headlight buttons and they work, but with speed zero set, it just runs on the track at about speed 8-10 until i remove track power. It does not respond to any speed command, nor E-stop. I have tried changing the address (while it's running) and it will stop briefly to respond, but then starts again.
Any ideas? Other locos/decoders work fine.

[jward]

It sounds like the decoder thinks it is on DC powered track and is responding to the track voltage. If you can program the locomotive, you can disable analog conversion in CV29. Analog conversion is a feature in decoders that will allow them to run on a DC powered layout. Unfortunately, sometimes the decoder can be tricked into behaving like it is running on DC while it is on DCC with the results you see. It's scary when your locomotive takes off at full throttle and won't respond to commands. Disabling analog conversion prevents this.

https://www.2mm.org.uk/articles/cv29%20calculator.htm

[tscroz]

Thanks for the advice. I will look into that. But when i read the track voltage with my multimeter, it reads 0.1Vdc and 12Vac. So if it thinks it is in DC mode wouldn't it barely have power to move?
I tried programming CV8, while it's running around my loop, but no effect.
I tried Decoder Configuration on the NCE PowerCab to turn off DC mode, but again no effect.

[jward]

DCC is hard for a standard voltmeter to read. It is not sine wave AC. It is square wave AC and the decoder's analog function circuitry sees it as pulsed DC when it doesn't detect a DCC signal. That's the simple explanation.