Märklin Digital for Dummies ^® Power Supply

How much power do we need? Well, as you will see in the Loco Decoders section, as a general principle you use only one transformer for the complete layout. If using the Märklin Control Unit 6021, you get use of 52 VA (approx. 52 Watts) maximum per transformer. If your transformer can provide more VA, you can use them for lamps in buildings etc (i.e., not via the Control Unit). You can start with using your old transformer, maybe it's 16 or 32 VA? A locomotive will consume between 9 and 12 VA, and everytime you switch a Solenoid, you use about 8 VA more. This list is provided from Märklin's own table in the "Beginnig with digital" handbook:

As described in the Solenoids section, I have tried to save some power in the turnout and signal area. However, if running more than 3-4 locomotives, and the 52 VA isn't enough, you can connect additional transformers to your layout using a booster. Never, never, never try to boost power by connecting your transformers e.g. in parallel; Clarifications:

The cost for a new Märklin Booster 6017 is about 1600 SEK / 160 USD (2002). However, I am using a Märklin 6604 Delta Control as a booster instead, after learning about this e.g. on the Bogobit site. You should find a 6604 at about 200 SEK / 20 USD.

My Power Supply configuration (as above) provides 82 VA to the layout; 52 VA is provided by the Märklin 6002 Transformer (feeding the 4 Occupied Track Feedback modules / 32 tracks and the main switchyard) and maximum 30 VA can be provided using the Märklin 6604 Delta Unit as a Booster (feeding the Solenoid decoders, i.e. turnouts, signals etc.). As all solenoids are controlled and operated via the booster, 4-5 locomotives can run simultaneously. Additional Märklin 6604 Boosters can be added according to the same principle. This is no hocus-pocus, the setup has also been presented by the Märklin Club Magazine (5/2002).

A Märklin 6647 32 VA Transformer e.g. could replace my Märklin 6611 40 VA Transformer. A Märklin 6051 Interface can of course replace my 6050 Interface, as well as an Uhlenbrock Intellibox can replace both the Märklin Control Unit and the Interface together.

Please note the following:

I have also tested to feed one of the Occupied Track Feedback modules with the Booster instead. The inner rail is isolated at the connection point between all 32 tracks. However, the red output from the Control Unit is then connected to the red output from the Booster via the engine pickup shoe, when the engine  is passing the connection point between tracks A and B powered by the Control Unit and the Booster respectively. Is this a problem? A friend from Märklin Mailinglist, Siegfried Grob, explained to me that this is not a big issue, as the Booster boosts the signal from the Contol Unit. A temporary bridging is acceptable, as signals are equal.

If signals differ slighty in amplitude, the difference in voltage will lead to a "cross current" from the higher voltage output to the lower voltage output, so effectively one output is partially supplying also the other, thereby increasing its own output current (maybe beyond limits) and relieving the weaker partner. This is tolerable if the difference is small and only temporary.

If signal for track A is independent from track B (like two separate Control Units, or Control Unit next to an analog track), the signal at the junction can be very different, even of opposite polarity. Bridging would make the two sources "fighting" against each other (like arm wrestling: the stronger one wins, or the arms stay somewhere in the middle with both players investing lots of power) like a short circuit. This must be avoided by the use of a pickup lifter / slider rocker in between.

My experience, testing feeding the tracks with the Booster, was that the locomotives sometime slowed down a little at the connection point. Therefore, I decided to let the Booster feed the solenoid decoders instead.