Brief Overview:
Starting in Digital; conversion of first loko (3000); ordered ESU Lokpilot mfx; dealer send me Marklin decoder from latest upgrade set - he doesn't know the part number of the decoder and there's nothing printed on it. I find out that it's not mfx; convert 3000 loko with hamo magnet only and test it with said decoder.
As I've read before the low speeds may be a bit jerky and sure enough they are.
I connected my Fluke scope meter to the motor signal and I see the following:

The important point here is the frequency of only 259Hz!

Now when I extend the time scale to see a larger time slice I get this:

Each of the grey blips you see occuring every 50ms is a bunch of pulses as seen in the first graph. It also reveals that sometimes it misses a set and the pulse groups are therefore 100ms apart.

No wonder this thing is jerky.[xx(]

One more test:
I disconnected the motor and ran the decoder without load on the output and the waveform was nice and regular - this leads me to believe that the "Lastenregler" (Load Control) feature which is trying to keep a constant speed no matter what the load is, is responsible for these variations. Maybe tuning the CV's I could get this problem sorted out - if only I had documentation on the CV's of this decoder! - and my LokProgrammer[:(]

Reading the ESU LokPilot mfx manual I can see that it operates at 40kHz, not the 250Hz I see with this unit.

Has anyone checked the output of other decoders to see what the ouput is doing?

If anyone else has trouble seeing the pictures please leave a post in this topic.

The problem:
The loko runs jerky at low speed.
I (and the dealer) can't identify the decoder, there is no number on it. All I know is that it came from Marklin.

My question:
Do all decoders suffer from this problem or is it onle the Marklin decoder(s)?
This is really a question for the techno gurus of this forum which can read the included graphs.

No pictures for me either... But what you are describing here is very interesting for me, because I believe the problem may be similar (or even the same?) to the one I posted here:

https://www.marklin-users.net/fo...ault.aspx?g=posts&t=4645

My guess would be that some (cheap) load-regulated Marklin decoders (e.g. the one from the pre-Christmas DCM conversion set, or the on-track programmable one installed in some Feuerwehr starter set locos) only work properly with the high-efficiency 5-pol motors; anything else (e.g. HAMO) and they get upset, angry and generally unwilling to play nicely.

Suggestion: try an Uhlenbrock or ESU decoder...

I will go for an ESU or Uhlenbrock decoder too. It's very difficult to work with a decoder you don’t know what is. And upgrade the motor to 5-pole makes it run just fine.

Hi moz,

Can't see your scope pics either. Your findings might have to do with the jerky behaviour of your lok. Perhaps the load regulation of the decoder does not work correctly with the 3-pole-DCM + HAMO magnet.

I have tested the motor voltage of some of my loks with an oscilloscope, too. Always found a very clean signal for older 6090x decoders (100 Hz pulse frequency) as well as for ESU/MFX decoders with 32 or 40 kHz pulse frequency.

Hans Martin