Fishmanoz

So that would seem to have interference suppression as its purpose, a choke in series doing much the same job as a capacitor in parallel.

blackbird, understand the suppression capacitor in parallel across the output and motor. The red black Cap in question though is in series with the input coming off one of the track pickups - see the instructions for fitting decodes to 0-4-0s on this site

Hadn't really thought about it, just installed the chip and noticed how far out the instructions were - the 2nd one was much easier as I'd already pulled the motor out for the first and that wasn't necessary. But it's unusual, the red/black capacitor is in series with the chip across the pickups and that component is not part of a "standard" configuration. It makes it open circuit to DC but has a small resistance at AC. All DCC feed is AC made up of DCC control instructions coded to each loco plus the power feed (AC too). Take a look at the DCC part of the Brian Lambert site for a good explanation. Not sure why the cap is needed for this loco type though as it's not needed for others. I could speculate it's like an AC equivalent dropper resistor as not so much power is needed by the small loco motor. Don't think it's an interference issue though? Maybe someone else has an idea? John

You could check it with a multimeter - it will show open circuit if it is a capacitor (capacitors are open circuit to DC and decrease in impedance as the frequency rises through them and in this case, impedance can be read as resistance - yes I know about the -ve 90 degree phase shift).

Howard, I think you'll find it is a black capacitor. I agree it looks a little like a resistor but they should have coloured rings being code for their resistance value or have the value stamped on them, but goodness knows how the Chinese may do it. You might also look at my reply 33 days ago in Hornby Collectors Club forum titled Collector loco (it's on page 2 there) where I give detail about how the actual process for fitting chips to the latest Collector 0-4-0s is different from the instructions on the web site - includes that the red capacitor is black. I think the web site may be a little out of date with current manufacture. Maybe HCC should check this to see if the web site should be updated?

Thanks everyone for the suggestions and, Western Fan, for the encouragement to try oorail77's. I must admit I didn't like this suggestion greatly as the frog is there to insulate, or you get a short across the rails as the straight track crosses over the turnout track - doesn't mean it couldn't be smaller though. But my first experiment just now was to check for track contact on the front wheels as the rear wheel was on the frog and guess what - no contact. I believe this is morairamike's problem - twisted chassis - rather than 00rail77's dip at the point of the vee because it happens at the other end of the vee initially and continues right along it. And it was possible to make it restart by twisting or pushing from the top over the front axle. I'll have to do some more experimenting with the 0-6-0, especially the fact that it stops with each of 2 axles on the frog (goes again between) as I can't figure the non-contact logic for this. And I'm still wondering about buying better quality 0-6-0s (Terrier) and whether I'll get the same problem again. Any thoughts on this anyone?

I've seen lots of people talking about the problems with running particularly 0-4-0 and 0-6-0 locos over point frogs but does anyone have a solution? For the purposes of this thread, can we assume that the rails and wheels are clean and the pickups are tensioned against the wheels, then concentrate on what problems might remain and how to fix them. If I can illustrate the problem from my own experience - I have 2 Collector locos; one runs perfectly, the other always stops when a frog is under the right rear wheel, showing that there is no electrical contact from the right front wheel. But everything is clean and the pickup is in contact with the wheel. What can be wrong and how do I find and fix it? I also have 2 0-6-0 locos (Mixed Freight so Railroad standard). One just runs like a dog, jerky all the time at low speed but it doesn't stop on points - I'm assuming this is just general bad contact but I'm not worried about this one because it's going back as it also has a faulty decoder (yes, I'm running DCC) which won't operate in reverse. More puzzling is the other 0-6-0. It usually (but not quite always) stops when the left middle wheel is on a frog, then it often restarts (not always) and sometimes stops again immediately when the left rear wheel is on the same frog. As far as I can tell, there must be bad contact between the wheel/s and pickup only at particular areas on the wheel, but I certainly can't see that area and polishing has got me nowhere so far. Any thoughts on that one? By the way, my Flying Scotsman Railroad works fine, I'm happy with that one. And a final question - am I likely to have the same problems with other 0-6-0s such as the Terrier class which I'm thinking of getting?