Perhaps the polarity of the transformers,if you are using two, are wrong. In the old Marklin handbook it shows how how to check for this. Basically take a 16v light bulb and jump the two circuits on the third rail with the power on. If it burns bright turn around the plug of one transformer 180 degrees and reinsert. Hope the helps- Fred

Thanks for all this helpful advice, Mike. Here are some quick answers to the questions, before I go and try out some of these tests after dinner...

1) Make sure that the red leads from the transformers are connected to A) the catenary and B) the centre rail (lead) and that the brown leads are connected to the track. Are you using a common lead for both transformers or do you have separate power supply tracks for each transformer? If using accessories, such as lights, signals or switches, how are these connected to each transformer? If you have accessories, disconnect each accessory one at a time to determine if this is the cause of your issue (by elimination).

>> I checked that all red wires are connected. I have two transformers, the brown leads are connected to each other, and the one red to the centre rail, and the other red to the catenary. I run all lighting on the one yellow, and all switches and signals to the other. I'll try seeing if any of the accessories are causing the toruble!



2) Do both locomotives have pantographs or is one a diesel or steam engine? If both have pantos, what happens if you switch power source for each locomotive?
If yes, are you running both locomotives with pantographs raised, even the one that is powered from the rails? If yes, lower that panto and test to see if that solves the problem.
Make sure that the power selection switch on both locomotives is correctly set to the selected source and not halfway between the two.

>> One is running on pantographs (SBB Ae 3/6), the other is a steam engine (DB series 38 -- my favorite, since I remember trip with that loco as child in the 1970s). I checked that all these were set correctly. I switched over the Ae3/6 to the centre rail, and it did not work either. So, I've eliminated the locos as the source of the problem.


3) What happens if you connect only one transformer at a time? Before testing, make sure that you disconnect the other transformer from the wall and from the track.
If there is a potential polarity issue, connecting only one transformer should solve that issue on that part of the layout. Perform the same test after disconnecting that transformer and reconnecting the other one to the track leads. If both work separately, it is likely that the issue is due to polarity.

>> I tried testing one at the time, but never thought to disconnect one from the wall socket. I'll do so.


4) What happens to a coach that is equipped with illumination powered from the rails? Are the lights on when there is power or does it display the same problem as the locomotive?

>> Coach lights to the same as the locomotive: no power at all, until I switch back, and then they light up very brightly. I eliminated the coach lights, and am certain that those are not the problem.


5) I forgot to ask which tracks you are using, the metal (M) or plastic (K) ones? The older M track catenary masts have metal bases that contact the ground and can short out if the live comes into contact with the ground. The catenary mast mountings for K track have plastic clips which prevents this.

>> All wonderful old-fashioned M tracks. If there was a short with the catenary, wouldn't the electric loco then not work as well?



6) The next thing that I would check is to inspect the catenary masts to see if any of the masts are warm after use. This would be an indicator of a possible short between one of the masts and the track

>> I'll check that.


7) If using K track, you should check the connection clips at the track ends to ensure that there is no short that affects the third rail circuit. If you performed test #2 and everything was ok with just one transformer, you can ignore this.

and lastly, If you don't do it for more than a few seconds, take the brown and red leads from the transformer connected to the track and swap them. That should have the same result as inverting the polarity at the plug. If everything works, then reversing the polarity at the plug should solve the issue.

>>> OK, I'll go off to my attic and try all this! Thanks for the advice, and I'll come back with a full report.

You both are right. It has to do something with the polarity. I measured and there is current between the red of the middle rail and the red of the catenary. Switching around the plug of the transformer did not help the issue: there still is current between the two. I completely disconnected the catenary transformer, and the problem persists, even though there is no longer any current between the two reds.. Any more suggestions? Could it have to do with the way I wired the ground? (They are all connected to each other.)

Mike: disconnecting the yellow wires does not solve the problem.

Thanks for the help so far. It gave me some helpful advice on what to look for !! If you have any more suggestions, it would be greatly appreciated.

Frans

Mike:

I ran all the tests you recommended, and I think I finally narrowed the problem down to the transformer itself, possibly in combination with a problem in the P8 (BR38) engine, which was not there before when I last tested it.

I switched the centre rail to the other (catenary) transformer, and while the P8 still had some trouble, the coach lighting seemed to work fine, and so did the Ae3/6 after I switched it to centre rail operation.

The other transformer switched to the catenary had the same problem with the Ae3/6 switched to catenary: it only changed direction but the 'normal' power supply did not do anything.

I finally made a small test track, and tested each transformer individually, with the Ae3/6 and coach running on it. The catenary transformer did fine, and the center rail transformer only reacted to the switchback function.

My P8 still seems to have some problems: when I run current through it, all the current seems to want to go directly to the switchback function. I think this might be something with its motor, or the brushes. I'll have to check the engine.

To answer your question below: the catenary transformer has a polarized 110V plug, while the other one can be plugged in both ways.

In short: the answer seems clear: I just need to get a new transformer. All your advice helped me figure out this very basic fact, but it also taught me a lot about polarity. So Mike (and Fred), thanks for responding to this thread.

Frans

Yes, they do. I'll take it apart and see what's up with the reverser. But first I'm waiting for a new transformer to arrive to power a test track!

Frans,

Glad to hear everything is working now. Enjoy the trains!

Harold.