Maerklin Transformer Issue

Maerklin Transformer Issue

By Roger Heid


Here is an issue that has popped up, here and there. I will devote this blog to clarification of an issue with the analog Maerklin Power Supplies with integrated speed control.

It has been noted, that there is a number of older folks who, upon retirement, decided to rekindle an old, long forgotten hobby. Old and dust covered boxes and cartons are re-opened, and an inventory of the contents is taken.

During the pre-digital times, transformer types like the one shown were in vogue. Over the years, they changed their outer appearance, but they were all blue in color. Their output power was pure AC (Alternating Current).


Now here is something you need to know. In the old days, Maerklin locomotives used a built-in relay to change the direction of travel. In an AC environment, switching the polarity around will not change the direction, such as it does in a DC (Direct Current) environment.

These relays required a lot more voltage than the 12 Volts present at the maximum speed setting. Something in the order of 24 to 30 Volts was briefly applied to these relays, at a short push on the throttle control knob. This brief overvoltage did not do any appreciable harm to the motors. The headlights would briefly light up very brightly, but these bulbs could survive this short abuse.

Now, if you merely use all the old analogue stuff you still have, you will be just fine with the blue transformers. But now you may have decided to purchase a new Maerklin locomotive, or any other make that runs on AC. Be advised, however, that about 15-20 years ago, after the introduction of digital control systems, Maerklin discontinued to install relays into their locomotives; the nature of the electric motors was also changed.

These new locomotives now contained a digital decoder to facilitate the use of digital control stations. However, these new locomotives could also be used on an analogue layout. This is still the case. Direction change is still accomplished with just a brief push on the control knob. But there is no longer this spike of excessive voltage.

The direction change is now handled by the decoder, which does not require this voltage spike. In fact, there is a very high chance that one of these old blue transformers will blow your new decoder to smithereens. Don’t use the blue transformer in conjunction with modern digital locomotives. If you still wish to maintain analogue operation, you need to switch to the newer transformers as pictured below.

Warning:  All these blue transormers made prior to the mid 1970′s have faulty insulation in the power cords. The rubber insulation by now is dried up and brittle. Fire Hazard!!


Maerklin #6646

That should do it, for now. I don’t want to confuse you with lengthy technical explanations. If you have any questions, please post them in the Forum under an appropriate topic. The Blog System is not geared to answer questions.

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