Hornby 7MT with a mind of its own?

[cameron_rayment]

I have a Hornby 7MT with digital sound 'Clive of India,' but somethings wrong with it. It works fine (and the sounds) for about 5-10 minutes then all of a sudden the sound stops working and it ignores everything I tell it to do. It just moves forward, quite fast, and the only way to stop it is by pressing stop. I have tried taking it off the track and putting it back on again but as soon as the tender is down and the driving wheels are on it just sets off on its own. Then I take it off until I go back, maybe a few days later, and the whole thing starts again. Anyone have any idea what's wrong?

[Chrissaf]

As long as you haven't got a Hornby Select controller, use your controller to disable "DC Operation" in CV29 (the Hornby Select doesn't support reading / writing CV29).

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When "DC Operation" is enabled, the decoder sometimes interprets a signal glitch (say a spike due to electrical noise or a transient short short) as a command to switch to DC. The decoder then sees the full always on DCC track voltage as if it is a DC voltage and the loco takes off. By disabling support for "DC Operation" this annoying habit can be (hopefully) eliminated.

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In order to understand how to use CV29 and what value to write to it to disable "DC Operation" see this web page that explains all.

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

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If your current value of CV29 is 6, then change it to 2

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Note: 6 is typically the CV29 default value, but cannot be guaranteed to be so. It will not be 6 if you are using 'long DCC addresses'.......see the posted link page for information on what all the numbers mean.