Loco runs at full speed as soon as it is placed on track

[Alan-363914]

Hi

I was wondering if anyone can help me

I recently purchased second hand the railroad dcc sound fitted tornado

As soon as I placed it on the track it runs full speed I can not stop it at all its like it's possessed :(

No controls work I can't re program it or anything

Any work around would be greatly recieved

Many thanks

[P-Henny]

Given that you state you can't see the decoder to reprogram it, then the most likely reason is that the seller has removed the decoder and replaced it with a blanking plate thereby reverting the loco back to being a DCC Ready (DC Analogue) loco. Shooting off at full speed is a typical observation of that scenario.

You will need to open up the loco and perform a physical visual check of the decoder socket. Do not place the loco on a DCC track until this visual check is completed and any missing decoder re-instated. Placing a DC loco on a DCC track will (sooner or later) damage the motor.

Note, if you lose sight of this thread, it will because a mod will have moved it to the 'Hornby DCC' forum where it should have been posted.

[ntpntpntp]

Ordinarily a DC loco placed on DCC trackwork will just sit and buzz. It will only move if the DCC system has "zero stretching" active which bends the DCC signal to run a DC loco. Some older systems had this ability, sometimes (but not always) called up as "address 0". It's an old technique not recommended at all nowadays, very bad for modern coreless motors.

Running away at full speed as described is more often a case of a decoder being present but not seeing a clean signal (maybe dirty track or wheels), causing it to revert to running as if on DC trackwork. That's why some people who only ever run their locos on DCC will program their decoders to turn off the DC support and prevent such runaways.

Anyway, in the first instance open up the loco as Paul says and verify there is a decoder present (or not)?

Have you got a DC controller you can try it with?

[Brew Man]

It's usually called DC runaway. You can and probably should disable it by changing the value if CV 29. if its value is 4 or more then subtract 4.

EDIT: Not quite accurate what I said there. DC running is enabled by setting bit 2 in CV 29. (The value stored in the register could be more than 4 without bit 2 being set). To disable DC running, bit 2 needs to be cleared. If you are unfamiliar with binary arithmetic there are tables to help.