Having accumulated four transformers (two blue and two white) that had constant power (for lights and so forth) but no power to run trains (controlled by the dial), I decided it was time to either fix them or throw them.

Fortunately I found the ~2004 discussion on this problem, and how to fix it. So I opened them.

The two 6646 white transformers both had wires that were broken at the sweeper, i.e., under the dial. I spliced in some Marklin layout wire and soldered it to the sweeper. Both now work. It is hard to avoid feeling that the wire used by Marklin is too light and/or rigid for the purpose, since both broke at exactly the same place.

The two blue transformers had no obvious wire weakness, but with these two examples in mind I removed the old wire connecting the sweeper to the lug and soldered a replacement wire in place. (During removal of one of the wires there did seem to be a weak spot near the sweeper, hidden by the casing.) Both transformers now work fine.

They are resealed and ready to use. We're not supposed to open them, but it is hard to see that what I did presents any safety issues whatsoever.

In a sense this is an update on that old discussion -- and thanks to those who contributed then -- but thought it might be of interest.

Bill

Would you be so kind as to post a link to the 2004 article? I have an old blue transformer that seems to be dirty inside. There are dead spots along the sweep of the dial. I'd like to know what I'm looking for before I tear into it
Thanks