# Frustrated with LGB 20581 Mallet DCC Upgrade



## LGB333$$$$ (Oct 11, 2017)

Hi Folks - I'm doing a DCC conversion on someone's older LGB 20851 Two Motor Block Mallet which has a Phoenix Model 97 DC/DCC Sound Decoder installed. He admitted he striped the idler gear in the rear motor block during a railway crash, and when I removed the motor, the damaged gears were obvious. I've done the following: Installed a Massoth XL Power Decoder; installed Massoth DCC Pulsed Smoke Generator; Installed 2 new Idler Gears in each motor block (front motor block also showed some damage too); installed new LGB/Marklin E126050 motors in each motor block which required bending the motor's electrical pins for proper motor block fitment (see photo); replaced two defective carbon brushes in front motor block.

Problem: The loco's motor blocks run smooth when operating on my Piko DCC Central Station test stand or when tested with DC power. But when I test operate the loco on my indoor DCC layout powered by my Massoth Command Station/Massoth Power Supply, the loco doesn't operate smoothly. There's a slight amount of continual surging noticeable at Navigator speed setting 1, 2 , 3 etc. I took the bottom covers off both motor blocks and realigned the wheels/gears to ensure there's properly meshing, no binding, and the loco still doesn't run smoothly. I can't figure out why this loco isn't running smooth as silk like all my other locos. What diagnosis am I missing.......advice please!


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## Dan Pierce (Jan 2, 2008)

Sometimes the BEMF needs to be fine tuned. Also the bemf setting for DC and DCC could be different. I have seen decoders where bemf is off for one or the other (DC vs DCC).
Since DC is OK, just find the settings for DCC bemf.


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## LGB333$$$$ (Oct 11, 2017)

Dan Pierce said:


> Sometimes the BEMF needs to be fine tuned. Also the bemf setting for DC and DCC could be different. I have seen decoders where bemf is off for one or the other (DC vs DCC).
> Since DC is OK, just find the settings for DCC bemf.


Hi Dan - This morning, just to play it safe, I replaced the XL Decoder with another brand new one. The first one I had used some on my one motor block test stand loco and maybe had made some CV adjustments to it too. I then put the loco on my indoor DCC layout and it ran much more smoothly than before........so it could have been the decoder. But this loco has been run quite a lot based upon the condition of the wheels. So I believe eventually it will need new motor blocks due to the normal wear and tear of the axles and their supports in the motor blocks.

So, I think your suggestion was also on the money.......it was the decoder's settings. Before I use that first decoder on another two motor block locomotive again, I'll do a decoder reset back to the factory settings which should resolve the issue.


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