Hornby Merchant Navy Class DCC hardwire question R2169 Clan line

[Buddy815]

Hi,

I have a hard wiring question to ask someone if they have hardwired an early 2000s Rebuilt Merchant Navy Class loco that is not DCC ready, so I took a go at it myself and wired the Orange and Grey wires to the motor and the red wires to together to the decoder and the same for the black. When I try to test the loco from the install, it errors out and there must be something wrong with what I did on wiring up the decoder. Does this model get it's negative feed from the track on the 2 wires from the tender and the + pickup from the loco? This is the service sheet for the loco in question. http://www.hornbyguide.com/service_sheet_details.asp?sheetid=295

I can take another stab at it but if someone here knows something on this loco, I would appreciate it. The loco seems to be fine in DC operation.

Thanks in advance if anyone replies to this post

Mark

[ColinB]

I have converted many of these. I must admit I generally wire them so the socket is in the tender, so I add the latest Hornby 4 pin connector setup and modify the tender to suit. The important bit is that on early Hornby locos the pickups on one side of the loco go to the chassis. I think it might be the red wire. So if you take the loco bottom off you will see a long casting in the shape of a pin on the chassis which when you screw the pickup plate on it connects the pickups on one side to the chassis. Now when I convert mine I usually file this down to about 2 mm long so it engages with the plastic pickup plate but not the pickups. I then attach a separate wire to the pickup. Mind you if you don't do this there still shouldn't be an issue. Check the bottom motor connection it is awfully close to the chassis so it might be inadvertently touching it. Generally when I convert a loco, I check that there is no continuity with the motor connections (orange and grey) and the pickup wires (red and black). In DC it doesn't matter but in DCC it will blow up your decoder.

[Buddy815]

Hi Colin,

Thanks for your reply, I am still looking at this, I put insulation tape on the bottom of the motor and it seems to have made things better, however when I connect the tender to the loco and I have the red wire that is screwed down to the loco, either of these 2 connected, it causes the short. So I think something is up with the tender as I can remove the red wire that is screwed down.

I do not see when I connect the tender how the short happens.

Mark

[Bulleidboy]

If your loco is shorting out with the tender connected it is possible that the pick-ups from the tender wheels are opposite to those on the loco - it was a fault on some early Hornby Merchant Navy Class loco's - loco is fine without the tender and as soon as tender connected you get a short. If you open the tender you will see the two wires (usually red and black) that go from the pick-ups to the tender coupling - on early models a pin with two bronze(?) fingers that are compressed during connection. If you reverse the wire connections within the tender that should cure the problem. I have had it happen twice, usually when using a different tender than the loco originally came with. If your a purist some Hornby M/N Class loco's have the wrong tender - on the real loco three types of tender were constructed, but Hornby only produced two types. I hope this is of some help.

[Buddy815]

So I opened up under the loco and I see that there is one red wire that is not directly connected to pickups on the loco. So it's like how is this working on DC, technically all it should be is one wire to one side of the track and the other to the other side of the track. I did remove the pick ups from one side of the loco and I am still having shorting with this loco.

[Bulleidboy]

Is the loco ok (running) without the tender connected?

[Buddy815]

In DC mode, it will not run without the tender.. I am not using the capacitor, not sure if I should install it now.

[Buddy815]

I did swap the wires in the tender and it still has an issue, can anyone explain to me how Hornby designed this loco and it seems there were a few more during that period to be wired as they did? I know they did not have any DCC ready locos then and they were moving away from the ringfield models during this period to motors in the locos.

[Fishmanoz]

Just on the capacitor - it is not needed.

[ColinB]

I have had issues in the past with the drawbar connector shorting out, that is one of the other reasons for using the later 4 pin connection arrangement. What I do in this situation is firstly wire up the loco for DCC, which you have done. Now check it runs Ok without the tender attached. Do all the checks for DCC, now try it on DCC. If it works then that proves your DCC is wired correctly. Now you need to examine the drawbar connector to check to see if it is shorting out anywhere, I have had so many issues with these connections. The trouble is with these old locos is the tender pickups over the years have oxidised and don't work that well, so you may well connect the tender and it works ok then suddenly the tender pickups work and cause the short. Another thing I do is put the loco on a stretch of track and lift the tender slightly so it doesn't connect to the track and see if the short disappears. Hope that helps. You are highlighting all the reasons why I rewire the pickups and add the 4 pin connector to the loco tender setup.

[Bulleidboy]

I think the wiring in the tender problem was just down to the individual who assembled the loco at the factory in China. I have thirty four rebuilt Hornby Merchant Navy Class loco's and they all run superbly. I have changed three tenders, which is where the wiring problem came to light.

Clan Line was one of Hornby's best selling loco's, with sales running into thousands. These "Super Detail" loco's were announced in 2000, so some time ago now.

[ColinB]

Bulleidboy you may be right but I do know I have had endless issues with those drawbar connections. I bought a Railroad A4 that had been detailed to look like a wartime black Seagull, really good conversion. It worked perfectly without the tender, add the tender and it shorted intermittently. I traced the fault to the drawbar, which is probably why I got it reasonably cheap secondhand. What I suspect happens is the connectors that stick up to connect to the flat copper PCB on the tender occasionally touch the pin.

[96RAF]

This is how the live drawbar works.

[Buddy815]

So I have put the loco wiring back as it was, except for the part I am trying to get a DCC decoder working on it, let's forget the tender for 1 minute, with everything in the loco back to factory, and I am not wanting to get power to the loco yet to test it as I am not sure if the decoder is will working correctly at the moment, should this part be ok?

[Buddy815]

Thanks for all the help on this one, so @96RAF that diagram you provided did a lot to resolve the issue, so the 2 red wires in the loco, do go to each side of the wheels and the tender does pick up from both sides. So with a multimeter, when I saw it from that wiring diagram, I was able to figure our what rail is for what side and wire the tender right to loco right and tender left to loco left wires to the decoder and it resolved the issue. DCC decoder is working!

I do appreciate the help on this one, hopefully if someone has a similar issue with a loco from this era comes across this post and it may help them