Hello Upperdecker,

this is not the first post regarding problems with the current Maerklin transformers. I presume that you have tested the transformer and that it is providing voltage from the brown and yellow sockets. You indicate that there is little or no voltage from the brown and red leads unless the dial is past the halfway point.

Maerklin's transformers have been sealed units for many years now. Many people have repaired their transformers by opening them up and then replacing the clips with other forms of fixation to keep the transformer closed after repairs.
You can consult the other topics for hints and details on how to open the transformer and get at the innards:

https://www.marklin-user...Transformer-Problem.aspx
https://www.marklin-user...ormer-problem--6667.aspx
https://www.marklin-user...sformer-Repair-Quiz.aspx

If the transformer is still providing full voltage via the yellow and brown sockets, it may be possible to use the transformer to power a 6021 digital control from it.
If your transformer is recent, I would contact your Maerklin dealer.

Regards

Mike C

I took the transformer apart and found the white wire from the red dial (aka the rheostat wiper) was broken under the wire insulation, possibly from metal fatigue or perhaps it had been pinched during assembly. I’m a little surprised that the broken wire gave such a consistent dead spot between the transformers indicated 50-150 power level and didnt just fail to work completly. Taking the transformer apart does not appear to be possible without drilling or using brute force to separate the halves. Marklin assembles the transformer using four little plastic dowels and I can’t see any way to separate the halved without drilling these dowels out or shearing them by prying the halves apart. For the re-assembly I used short #8 machine screws in the dowel holes. Hope this helps the next person who has the dreaded 6646 dead spot.

Hi Rich

I don't have a 6646 but I have repaired a 278 Transfo of 1953 based on the same principle: the secondary winding is coiled very precisely so a slider get various voltages from 7 V till 14 V.

You may replace the wire with a flexible, insulated wire suited for 1 Amp minimum if there is no doubt were to solder it.
Check the overvoltage contact and cabling
Make a resonnable length loop so there will be no stress on the wire after a long usage and the the loop will not get caugt somewhere while turning the knob.
Also, make sure to verifiy the power cord is not damaged especially if used by children.
Bonne chance

Jean

Although I've yet to experience this issue, I have often wondered: are there any Maerklin compatible transformers to consider when operating older, analog equipment?

Märklin 66471 is the current transformer for 230 V and it's available at the factory (66470 is sold out at the factory).
6646 is the current transformer for 120 V and it's available at the factory.

I assume the question is about third-party transformers. I don't know if Titan are still in business.
There are many third-party transformers for fixed voltages like 16 V, 15 V, 17 V, 18 V, but I'm not aware of current makers with adjustable voltage and the over-voltage pulses to reverse the direction.

This dealer shows Titan 907 as "in stock":
http://www.roundhouse.ch.../titan_transformator.htm
I don't know if they also offer products for 120 V.

The EU has requirements for stand-by power. A physical switch on the 230 V side ensures very low stand-by power.

US requirements are different.

It looks as if the 6646 vanished from the catalogue years ago and they only sell the remaining stocked items. Maybe a new production run (if any) will have the switch, too.