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DCC & my Run-Away Train


NERBOB

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Hi all, please can someone enlighten me?

I have a new decoder fitted to a Hornby Stanier MT

 

It's a Bachmann decoder, and I'm using the Bachmann Dynamis wireless. (No pro-box)

 

The Loco runs very well forward and responds immediately to the commands. All functions are ok; Running Lights, Firebox flicker, speed and slow to stop (forward). No problems.

 

As soon as I reverse the Loco, it runs well but doesn't respond to reducing speed commands, even if I return it to zero. It just runs and runs and runs, and runs..........(backwards) until it eventually slows to a stop (sometimes near 30mins).

 

So, just to reiterate:

Loco runs forwards and responds to all speed settings.

Loco runs backwards and won't stop, or respond to any setting of the throttle control.

(The only way to stop it when running backwards is to hit the "STOP" key, which is a bit abrupt and unprototypical!)

 

I don't have the pro-box (yet - still looking for one) so can't see/read or modify CVs

 

Any clues or advice please?

Ta. Bob

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This used to be a common problem, Runaways. With modern up to date decoders it should not happen.

There have been many suggestions as to why.

All i can suggest is, Reset the decoder to default. Loco 3. Then run it at this address and see what happens.

If ok then reset to your ID for this loco.

Just had a thought, have you set CV4 Deceleration, to high ?

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That might be true of a 'modern up to date decoder', but we do not know what is fitted. It is possible to have sufficient contact to provide power, but if the signal is interrupted bits will be lost. Since DCC has no error recovery the loss of one half bit from a packet makes the whole packet unreadable, and there are in excess of a hundred half bits in a 3-byte short address speed packet. 1% data loss will result in no packets being received, but 1% power loss will not be noticed since the capacitor will smooth it out.

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