Before we begin, a picture....

This is the loco as unpacked from the box.....  Ok, I had managed to touch it so one of the front lights is "bent"...  Delicate stuff, this Liliput.... Not as we are used to with our Märklin trains...  It is a Liliput L109100 in Preussian livery... It was called T9 during the Länderbahn era, and was re-lettered to BR91 in the DRG standardization days in "Era II"...  This model has no traction tires, but is heavy as a tank, since it is all-metal except for some detailing pieces...  It also has "Federpuffer", the buffers move when pressed... It also has a 5-pole DC motor that should guarantee smooth performance.... 

Remember this picture, as the following story is not as "pretty"...  ;-)


The procedure, as imagined..

Since this is a 2-rail DC loco, I thought the only thing would be to put a slider under it, and then rewire the loco for 3-rail operation by connecting the wheels together and then add a Lenz LE900 decoder to the NEM pocket which is on the PCB in the guts of the loco...   I was "a bit" optimistic with these thoughts.....  As Martin Silz says in the 3-rail DC article on this site - "The devil turns up in the details..."

Fitting a slider

I did several tries to fit a slider to this loco...  Everything was ok until I tried to run it across K-track turnouts....  Then the loco was lifted off the track by the raised center studs in the turnouts....
Ok, I thought, it's just a matter of some mm - so I "shaved" the bottom plastic plate as much as I could, and even cut away most of it while experimenting....  Still gets stuck on the turnouts....  I also consulted Mr. Silz who has done several similar slider mounting tasks...  We did not manage to get a working solution for this particular loco, so I decided to do a "ghost-wagon" solution to solve my problem...  This means you put a slider onto a wagon which is the first after the loco and you pull a cable from the slider to the loco from that wagon.

The pictures below show the original slider mounting place (clear plastic piece) where I mounted the "short" loco slider (7164), then the massacred bottom of the loco, and finally the "ghost-wagon" (a Roco baggage wagon) with a 7185 slider mounted... 





The Dremel tool came in handy to make holes for the cable in the wagon....  Every modeler should have one, or a similar handheld tool....


Let's get into the loco....

The loco consists of the pictured parts, as you can see there is also a PCB where the electrical wiring is...  This PCB also has a NEM digital connector...  After dismounting and remounting the parts several times, I noticed that the wiring was really not up to normal "Märklin" standards.... The PCB was insulated to the chassis with plain clear tape in several places, and this got worn out after a few assembly sessions - causing shorts.... (Sorry about the pic, out of focus...)...




So what did I do ?

Since I had these "shorting" problems I ripped all the "guts" out, only leaving the motor...  Then I did what you would call a "normal" conversion, soldering the decoder leads directly to the motor, lights etc...  Here below you see pics of the decoder mounting...

My son had to sacrifice a small piece of Lego...  This was then milled down so the decoder would not be too high up and touch the metal loco body... Please also note the clear plastic pieces that will prevent the cabling to get messed up in the worm gear... This is all done with acrylic "superglue".... The loco is really small, as you can see by the size of the "thin two-dot" Lego piece.... 

  

The decoder is also glued into place....


   

Ok, after connecting the motor, it is time for a test run but some obstacles are encountered doing this...  Lisa (one of webmaster's two cats) is blocking the track quite efficiently....



"Ok, I will let it pass, but I will check the wiring extra carefully for you"...




It works... but...

Ok, now we tidy up the wiring, and here it is...  Should work nicely...




So what's the "but" about then ?

Well, those who have read the "2-diode conversion with LE900" will recognize this....  Suddenly the loco stops or runs at "full speed", jumps, flashes the lights etc....  Is it a short ? - No...  Is it overheating ? - No...    The phenomenon is even worse here than with the "2-diode" conversion....  
In the picture above, you can see that I have mounted an extra capacitor, as I did with the "2-diode" conversion in the end, but it did not help much....  So obviously the interference did not come from motor poles...  I then mounted an inductor (coil) in series with the slider connection (as Märklin's 60901 kit has) and the problem disappeared...   It seems like the Lenz LE900 is extremely sensitive to sparks etc, and requires extra "noise-suppression", either from the motor or track current...  


Finally...

It runs as expected followed by its "ghost-wagon", but since the loco has not traction tires, the pulling ability is "somewhat" limited... 



Summary

It was a very educational conversion indeed...  Was it worth it ? Well - to be honest, not really since the loco is not a good puller (no traction tires and a DC motor that is not quite up to Märklin standards)...  But with an axle with added traction tires and a "load-regulated" decoder as the 6090x (Märklin/Motorola) or the Lenz LE130 (NMRA DCC) it would probably be a real gem...  The next project will be to add traction tires to this loco...  The Dremel tool might come in handy here too...  ;-)