Hello there.

I have recently laid a double track parade layout around the circumference of my train room, as an adjunct to my Gauge 1 layout, dimensions are 20ft by 12 ft so two decent runs with long trains. I have used K track, mostly new, the two circuits are connected by high speed points at four places on the layout. (Two on each side). These points are all electrically isolated from each other (by cutting off the center rail connectors, I don't trust those plastic things) so the two circuits, while physically joined, are electrically separate. As I have a lot of analogue locos, I want to get it running perfectly on analogue, before introducing digital switching later.

I have installed 2mm bare copper wire buses beneath the layout, a separate power feed bus (red wire connections) for each circuit. I was told that I only needed a single bus for the earth connections, i.e. all brown wire connections from the two circuits could go to a common bus.

However, I am being plagued by issues with only parts of each circuit currently running. I have been through a fault finding process, writing each step down as I go and retesting. Just now, I decided to power on one of the two transformers only, that for the outer circuit with the other (inside circuit) transformer turned off at the mains switch. I then connected the EARTH (brown wire track connection lead for that circuit) to the turned off at the mains transformer and - guess what? IT POWERED ON! While still being off at the mains!

My question is: was I wrongly advised that I needed only a single earth bus for both circuits (this was a digital only operator who told me this) and for analogue, do I need a separate earth bus for each circuit?

Or is there likely something else amiss? ( I have checked that all joints in the copper wire are correctly connected to their respective other sides where modules necessitate a joint).

Sorry, but you have misunderstood me. Nothing illegal about what I'm doing, not plugging anything into the mains power plugs other than the two transformers themselves. Here in New Zealand we have 3 pin plugs and these trafos have their factory fitted 3 pin plugs, so polarities must be correct. When I said "connected to the TURNED OFF at the mains transformer, it was not to the mains socket (!!) but to the trafo's own earth output.

From what you say, it must be that I have some red wires crossed somewhere between the two circuits. Good to have confirmed that I only need ONE common ground.

Not entirely uncommon, makes soldering dropper wires much easer

Many thanks for the thorough answer Steve, much appreciated. I hadn't thought of what you outline in your opening sentence! I'm off out soon to purchase a couple of plugs, then cut off the moulded plugs and replace with both hooked up the same way.

I'm not sure how to open the plastic cased trafos but hopefully I won't need to do this. If the problem still exists after I have fitted new plugs, the problem must be the internal connection within one trafo, not matching that of the other (colour coded wires) so I'll swap the two primary wires over in one of them.

Will keep you posted. thanks again.





quote=cookee_nz;666179]

Hi Allan, all....

My take on this is that although the transformers were wired from the factory, they can still be out of phase. I've had it several times. I'm not sure whether Märklin could even establish a 'correct' polarity for countries like us with oriented plugs.

Although the feed going INTO the Trafo is colour coded Brown & Blue, it's how the feed to the Primary transformer core INTERNALLY is done that can make the difference.

I check all my Trafo's for polarity and standardise them. First thing is you need to decide which Trafo is your template to match to. If you have several that becomes a challenge.

When I did mine, some time ago, I had a single WHITE Trafo 52VA which came with my original digital set. So I decided that would be my "master" and I matched all others to that.

The downside is that I have some Trafo's that have the phase and neutral reversed in the plug, but I put coloured heat-shrink over to make this very clear. I also added a strong label onto the cord at the plug with a comment.

The other really easy way you could achieve the same thing would be to make yourself a short (6") adapter 'extension' cord, and change the phasing in that rather than the Trafo plug. Using a brightly coloured cord, and a very clear label that the cord is phase-swapped to be used ONLY for the Trains.

Either way, if the original plug is a moulded one you are going to have to cut it off and replace with a screw type, Tap-on etc.

The only other way you could do it to avoid wrong colour coding would be to open up the Trafo and reverse the wires for the Primary winding input. That would achieve the same thing, and I have actually done this when replacing the mains cord.

It's become much less of an issue lately with the uptake of Digital, but there is also a strong remaining passion for the vintage stuff and this is where people, (newbies in particular) can trip up.

Oh, and of course, there is a third option. If you have several Trafo's to choose from, just find two that are the same and use those

Hope that makes sense. If you resolve the phasing, I think you'll be ok.

Cheers

Cookee

Hi Tom,

Yes I agree that this appears to be a two-pronged issue (pardon the pun re the European plugs)

In an ideal situation it would be *just* the crossover location being bridged, but because it appears to be independent of that scenario, there still remains a possible hard-short somewhere between the two circuits, yet to be located by Allan.

I've seen elusive short-circuits caused by staples, screws and nails through wires. In one instance, a track-screw had gone through the base-board, and the sharp tip had only just penetrated a wire directly below.

Because of this, it was not visible from any angle, and it was M-track so the screw was 'earthed' via the trackbed, but the wire was a 'hot' side, track or lighting I can recall which. I can tell you, THAT was an extremely difficult issue to pin-point because it was intermittent.

I think there was a combination of temperature, vibration, and a circuit that was not always active making it hard to isolate. I've also known of stray screws and staples being caught underneath track and causing short-circuits.

Allan, if it continues to elude you, it may come down to having to physically lift some track in order to separate some sections to help isolate. "Divide and conquer". Sometimes you spend longer trying to find the issue with everything in place, than just biting the bullet and start lifting.

With any luck you'll find it early. If there's no ballast, it's a heap easier, and being mostly new track should help as well.

Good luck

Edited by user 20 November 2023 09:44:42(UTC)  | Reason: Typos

Actually, I just realized Steve, that these two transformers, which I bought new are the same ones I used without any polarity issues on my M track layout. So I think I'll leave changing the plugs for now and go with Plan B, as above!