Strange behaviour of a King Arthur

Discuss Hornby Model Railway products and related topics here. This includes (Lima, Rivarossi, Jouef, Electrotren).
UrbanHermit
Posts: 284
Joined: Wed Jul 09, 2008 11:18 am
Location: Back of beyond, South Wales (Isn't it?)

Strange behaviour of a King Arthur

Postby UrbanHermit » Sun Mar 21, 2010 12:40 pm

The last time I got a chance to play trains, last Sunday, my N15 started doing something rather odd.

The loco was bought last Christmas and is therefore only about three months old. It was fitted by the vendor with a common-or-garden Hornby decoder. So far I have been very satisfied with it - beautiful detailing and a lovely runner.

Last Sunday, after setting up the layout and starting the trains rolling, I was in and out of the room, leaving my son to do what he likes doing, watching the trains go round. So the N15 had been running continuously for well over an hour, when I came into the room just in time to see it suddenly screech to a halt without anyone touching the controller (Hornby Select), reverse for about two feet, stop again, and then carry on forwards as if nothing had happened. When it came to the opposite point on the oval it did the same thing again. This happened two or three times, always at the same opposite places on the oval, before I stopped it. All this time my son's train had been running normally on the other track.

I left it stopped for a few minutes, and when I started it up again it seemed to be running okay; but at this point I had to clear everything away so we could have dinner (it's an on-the-dining-table layout), and I haven't had a chance to get it out again since and see how the loco is behaving.

Does anyone have an explanation for this rather strange behaviour?
"I fell out of favour with heaven somewhere, and I'm here for the hell of it now." (Kirsty MacColl)

Bigmet
Posts: 7933
Joined: Tue Aug 14, 2007 2:19 pm

Re: Strange behaviour of a King Arthur

Postby Bigmet » Sun Mar 21, 2010 6:16 pm

That is most likely some sort of glitching in the signal the decoder is receiving. I doubt there is anything wrong with the decoder, since it is still functioning. The clue I think is that you had the train running for an hour, on what I take to be a set track layout - is the track loose laid? If so then what I would surmise is that track joints had started to loosen, and electrical continuity was being lost momentarily as the loco ran over. When a decoder looses power it it stops the motor pretty much dead. Now, between the Select, any capacitors in the network and the track connection, the signal was corrupted to generate an opposite direction command. The decoder obeyed this, then got the correct signal on a well connected piece of track, and ran forward through the trouble spot.

Notice I mentioned the Select as a contributor. When Hornby introduced this unit as their low cost entry to DCC it was quickly found to have a signal form which made it non-compliant with the NMRA DCC specification. I have read similar descriptions from Select users in the past; this unit appear to be very sensitive to any interuptions or disturbances in the track supply. If you ever see this again, check how well the rail joints are made in the location the loco had just gone past, wherever it shifted into reverse.

UrbanHermit
Posts: 284
Joined: Wed Jul 09, 2008 11:18 am
Location: Back of beyond, South Wales (Isn't it?)

Re: Strange behaviour of a King Arthur

Postby UrbanHermit » Mon Mar 22, 2010 12:53 am

Thank you, Bigmet, for the (as usual) lucid and interesting reply. I am indeed using Setrack, but it is pinned down to a baseboard. Nevertheless, I will check the connections.
"I fell out of favour with heaven somewhere, and I'm here for the hell of it now." (Kirsty MacColl)


Return to “Hornby - including Lima, Rivarossi, Jouef, Electrotren”

Who is online

Users browsing this forum: Google Adsense [Bot] and 7 guests