Hi friends,

This weekend I converted my Amtrak F7 double unit (33621) to digital, using a Lokpilot V2.0 decoder. This is somewhat challenging as the decoder has to supply two motors here. The lok comes with two 3-pole DCM motors (AC, with field coil) and a 6603 delta decoder. The conversion was necessary as the speed and load characteristics of the 33621 was not sufficient for my purpose, and digital brake sections were not supported by the 6603 decoder.



After a complete disassembly of the lok



I installed two high performence motors using two 386820 5-pole rotors, 386940 motor shields, and 389000 field magnets



Connecting each motor to 10 V DC shows that the idling current is quite low (0.14 A) but increases to more than 0.65 A when I braked the wheels with my thumb. This gives more than 1.3 A in total for the two motors. So I was a little worried that two motors switched in parallel could exceed the max output load of the decoder which is 1.1 A. However, I proceeded keeping in mind that I might have to solve a problem at the end of the conversion session.

After installation of the motors the lok got a 8-pole interface as is common on DC locos, as the Lokpilot decoder comes with a 8-pole plug. Funny to see, the interface plug is larger than the whole decoder. Well, there is plenty of space under the F7 hood, no problem. I must say this 8-pole interface is a very comfortable invention: no soldering at the delicate decoder wires, and the decoder can easily be removed when soldering has to be done inside the lok.



After sewing the bunch of wires inside the lok together



the casings can be mounted again, and that's it ! Total cost of decoder and motor parts: 75 EUR.

The lok runs very smooth out of the box, no change of the load regulation CVs (53, 54, 55, 56) required. I only reduced the max speed from the default value of 64 to 25 (CV 05), and the medium speed from 22 to 15 (CV 06). Speed is now more or less prototypical.

I have tested the lok with quite heavy trains and on grades: power consumption is far below the decoder maximum current, and load distribution between the two motors seems to be o.k. Moreover, the lok can handle the simplified brake section which we have discussed in another topic some time ago. That's good news.

The F1 and F2 functions of the decoder are still unused presently, but I'll install switchable electric couplers for passenger car lighting and perhaps some kind of mars light.

Hans Martin

Sweet Hans Martin!

I have no plans for such a conversion but it is very interesting to read about, and such great pictures. Glad it all worked out so well for you, a reward for all your planning.

John

Most interesting conversion, Hans Martin - congratulations [:p] !!!

Nice conversion indeed.
And nice loco's too.
A powerful combination (multi traction).

Timaximus

Thanks Hans Martin for sharing the exemplary article for a professional job on a great model!

That's just what I need to do next for my ABBA -setup. Do you happen to have the numbers for the parts needed with SFCM -motors? https://www.marklin-users.net/html/service/SEmotors.html
At least the SFCM and DCM engine housings have different numbers according to Märklin parts site.

Märklin seems to have a special set 60760 for older engines, and a set 60904 for "most" flat collector motors. Do you have any experience with those?
Please see their website @ http://www.maerklin.de/produkte/digital/umruest.php and
http://www.maerklin.de/produkte/guenstigwienie.php.

For those who don't follow "Building kits & kitbashing" -forum, there is a couple of F7 topics related to this one.

BR,
Juha'