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Ever since I (the webmaster) started
out with digital, I have planned to convert my childhood locos to
digital. I have been reluctant to do this, since I have been
"emotional" about these and especially about my first loco
ever, a 3003 that I got for Christmas in 1963. This loco has been with
me since then, and every time I have taken it out it has worked as it
should. It was stored away at my parents house for about 20 years but I
got it back when my son got his first railroad a few years
Since I have done the 6090 + HAMO
conversion before and have blown decoder motor outputs, I was a bit
reluctant to do it again. Also, I did not have a HAMO SFCM magnet at
home... What I had at home were a few Deltas and a Lenz LE900
decoder for DC motors.... So I decided to make down right
dirty cheap conversion with the LE900 using 2 diodes to rectify the motor
current.... The 2 diodes trick is a well known way to make a
Märklin loco run with DC power... You replace the electromagnetic
reversing unit with 2 diodes and you can then use the loco as a DC loco
instead... The electromagnetic stator in a Märklin motor has 2
coils, one used for each direction. It has 3 leads, one is going to the
motor and the 2 others are connected to the reverse unit. The connection
setup is well described by this picture, taken from the Ames-Friberg-Loizeaux
"Digital Command Control" book published by the Swedish Allt om Hobby publishing
company. (BTW, this book is recommended even if it is about DC-digital,
not Märklin digital)....
This is what I started with.. 1 childhood loco, 2 1N4001 diodes, a Lenz LE900 decoder, a piece of clear plastic, some straps, "superglue" and of course a soldering iron....
First of all I had to clean the loco a
bit, since it had about 30 years of stale oil, dust and cat hairs in
So now it was time to re-mount the
motor, and connect it to the diode setup. I had some problems with the
stator coil winding ends, since they were old and broke where they were
connected, but I managed to connect cables to them after all...
Then I tested the motor in "DC mode" by connecting it
temporarily to the digital test track... The motor was ok.... It
moved in both directions....
Finally, the loco was tested at what it is intended to do, and that is pulling a few "Thunderboxes" around on a digital layout....
Summary and peculiarities
The Lenz LE900 seems to have the same
capabilities as a 6080 or a Delta, since it has no EMF speed regulation
as 6090x. However, it has adjustable acceleration an
deceleration. My test run was made with the factory default
settings for the decoder and the loco ran very well indeed...
Actually far better than Delta. I will test with the programmable
settings later on... I was rather impressed by it since it is a cheap
decoder (about the same as Delta) compared to Märklin and Uhlenbrock decoders.
After some more testing, it seemed like it got some "overheating" problems, since the loco suddenly started to jump and at the same time it flashed the lights, even if the lights were turned off... This could of course be a case of bad connection, or because I connected both light outputs to the front light, or it may be a general problem with the setup since 2 diodes do not provide perfect "DC-power"... I will have to investigate it further. A Märklin decoder would probably have been "fried" under the same circumstances.... Even if the speed is set to zero, the loco continues to jump.... But if it is lifted off the track and then immediately put back again, it runs normally for a while again.....
Probably the decoder is ok, but the wiring might need an overhaul. I will investigate and test some more regarding this matter. Since the function outputs are protected, I have a suspicion that it doesn't like my wiring with both function outputs connected together.....
This page will be updated as soon as I find the solution to the problems I have noticed...
But in general, the decoder runs very
well indeed and the peculiarities mentioned are noticed only after
long-time continuous running...
Update regarding the
It was a simple solution to the peculiarities, but - in general, it is recommended in Lenz manuals to get rid of all capacitors when installing one of their decoders, so it was not the obvious choice. Since this is not a decoder with EMF load regulation, it doesn't matter. With EMF decoders as e. g. the Lenz LE130 (NMRA-DCC) a similar solution would probably not be applicable due to the impact on the EMF signal.