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Discussion Starter · #1 ·
I saw a posting from Dan Pierce I believe some time ago about the older versions of LGB Buhler motors requiring a special CV setting to make them operate better with a DCC decoder, but I can't find it. I just completed a DCC sound conversion on a customer's LGB 2174D using a Massoth XLS sound decoder. It has the older version of the Buhler motors but it was operating fine in DC analog power. I tested the locomotive after the installation and get some very slight jerky movement at the lower speed steps. I tried various adjustments to CV2 starting voltage but that didn't help. So, I turned off the CV49's digital control and left it to just CV49=1 since the customer still uses the old LGB MTS system and 14 Speed Steps. As I've experienced before, and other hobbyists have also encountered, turning off Digital Load Control makes the the motor run smooth as silk but then increases speed too much between Step 1 and 2 etc. So I tried all types of combination settings using CV2, 5 and 6, but still can't reduce the high speed increase between Step 1 and 2, etc. Yes, I know that using Speed Steps 14 instead of 28 is part of this, but I've set a lot of decoders for 14 Speed Steps and there's not such a large increase in speed between 1 and 2 as this motor is doing. Is there another CV setting I should be also using for these older Buhler motor to make them operate well particularly in Digital Load Control is ON or OFF. The customer is retired and on a tight budget so I don't want to replace the older Buhler with a new motor. Thanks!
 

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Unfortunately, I think you answered your own question... 14 speed steps are just too coarse. So the question about perhaps lowering the top speed (and of course picking a right mid speed setting) is apparently answered.

I would lobby for a lower top speed. Unfortunately, old stuff is exactly that, old stuff.

Greg
 

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There should be no difference between an old 7 pole and a new 7 pole Bühler motor—they are both capable of excellent low speed performance. Also, 14 speed steps isn’t the issue—since most decoders interpolate between the steps with enough momentum set that will not cause the jump you’re looking to eliminate. I’ve found that with Massoth decoders you have to make your own speed curve, and also to spend time with the BEMF CV’s that control how hard the BEMF hits, how long it hits and the rate etc...sorry I can’t recall the exact CVs but if you look in the Massoth manual you will see their explanation along with a graphic representation of each and what it does. With enough time you should be able to get it very smooth. Ultimately the limitations of each decoder will become apparent. My smoothest low speed control is with Zimo and also the new Maerklin MFX decoders are excellent if you spend the time to fine tune all the various Cvs. Good luck...just take your time as it takes a lot of iterations but keep that old motor—it will outlast the newer ones by a long shot!
 

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Also forgot to mention, that it helps to “compress” the available speed steps by lowering the top speed as Greg suggested and then make the speed curve more parabolic rather than linear.
 

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Discussion Starter · #5 ·
Thanks for all the excellent advice. After spending an hour trying numerous CV settings with Digital Load Control OFF and found it not so good, I decided to go back to Digital Load ON. Below are the final settings I made and she operates with only minute occasional jerking at Speed Step 1 and 2 that only a keen eyed perfectionist like myself would detect. I asked my wife to watch the loco on my test track and she didn't see any jerking movement. So I'm done and shipping this loco back it the customer. I made a short video of it on the test track but unfortunately can't easily share it with everyone without posting it on my YouTube Channel which I don't have time or motivation to do.
  1. CV2= 7 (default 2);
  2. CV3=7 (default 3);
  3. CV4=7 (default 3);
  4. CV5=200 (default 200);
  5. CV6=60 (default 50);
  6. CV29=0 14 Speed Steps (default 4);
  7. CV49=3 Digital Load Control & Parallel/Serial Function Data (default 3);
  8. CV197=20 Chuff Duration (default 8);
  9. CV198=32 Time Between Chuffs (default 32).
 
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