Fitting a decoder to a Hornby Bullied Pacific

[Foreland]

I have a Hornby Rebuilt Merchant Navy Pacific, it is not DCC ready but has a modern five pole motor. I have fitted an eight pin socket. On test the loco runs perfectly on DC but is unresponsive when I fit a DCC decoder. Any advice would be gratefully received.

[34theletterbetweenB&D]

The most valuable information will be what read out (and its meaning) you obtained when tested on your DCC system's programme track. It could be as simple as 'no decoder detected', usually a dry joint or possibly a wire break between the loco pick up and the red or black decoder terminal.

[Mallard60022]

Deffo check your wiring set up to the Decoder Socket first. I don't know how you check if trickery is flowing to it; some sort of Meter? Also as 34 says.

Phil

[RFS]

You say it runs perfectly on DC. Does this mean you fit a blanking plug and it works? And you then replace this with a decoder and it doesn't? If so, I would check with a meter that the pair of pins at each end of the socket are not live to each other. This would cause a problem for a DCC decoder, but not under DC, as the blanking plug simply joins them together anyway. 

[Butler Henderson]

Would be simpler just to hard wire a decoder.

[Foreland]

Thank you Robert. You are right, I have fitted a blanking plug and then replace it with a decoder. I run a check on the pins and see what transpires.

 

Cheers. John.

[Right Away]

I’ve no experience of the Hornby Rebuilt MNs, but you state yours is not one of the DCC ready (later) versions; could there be a possible issue with the chassis conducting?

Just a thought.

Edited January 19 by Right Away
punctuation

[SRman]

I have done a couple of Bulleids (MN and BoB) that were pre-DCC-ready versions. I directly hard-wired them with no socket at all. The live return goes through the chassis, but I had no problems with that. The red and black wires went to the separate pickup and to the chassis ground screw (I can't remember which went to which at this time), and the orange and grey to the brushes, which are entirely insulated from the chassis anyway - the original wiring had a wire going from the chassis using the gearbox top screw, so that's what I used when putting the decoder track wire. 

[John Clitsome]

I did this with an old Hornby Princess and found it best to hardwire as previously advised.

[Foreland]

Problem solved! Thanks for all your advice chaps, I rechecked everything, including looking for short circuits, none appeared and then I tested with a decoder borrowed from another loco and everything worked fine. I think the problem is most likely in the simple decoder I use for testing before fitting sound ones. It looks like a £35 replacement test decoder is the order of the day.

 

John.