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Thread: DCC Decoders

  1. #11
    Senior Member DiveController's Avatar
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    Quote Originally Posted by Noel View Post
    BEMF Tip for Laisdcc decoders

    It is better to have BEMF on for smooth slow startup and smooth stopping or crawl speeds, so rather than turn BEMF completely off to avoid the speed surge issue mentioned earlier in the thread, you can have BEMF on but only below speed step 12 which avoids the speed surge problem when stepping down below step 24 (i.e. assuming you are using the default 28 speed step mode).

    • CV61=1 (BEMF ON)
    • CV10=12 (BEMF speed step cut off at throttle step 12)


    PS: Apologies for not adding this to my original post a few days ago, but I missed the edit window.
    Many thanks, Noel, for your continued testing. Can you elaborate on the speed step down surge?I did't fully understand the issue.
    I haven't run my 141s in a while.I thought there was independent control via switches 'under the hood' (very troublesome) or by DCC?

    Quote Originally Posted by Dave View Post
    I don't think they have been tested with automatic brake control, but I'll ask the manufacturer.
    Any update on this?
    Last edited by DiveController; 11-01-2017 at 03:00 AM.
    "Where Seventeen Railroads Meet the Sea"

  2. #12
    Quote Originally Posted by DiveController View Post
    Many thanks, Noel, for your continued testing. Can you elaborate on the speed step down surge?I did't fully understand the issue. I haven't run my 141s in a while.I thought there was independent control via switches 'under the hood' (very troublesome) or by DCC?
    Hi Kevin. Ok, this is going to read a bit long winded, but its an easy fix.

    TCS M4 decoder had a slight 'surge' problem when BEMF is on. When reducing throttle steps from 28 down the loco would slow accordingly for each step, but when passing down through throttle step 23 or 24, the loco would slightly speed up again (i.e. surge), and then slow as you continued to step down past step 22 and below. This effectively put a what looked bump in the speed curve irrespective of the setting of CV6 (mid voltage), or even if you had proper user speed curve defined. This is a know issue with the TCS that the Laisdcc inherited which was caused by a bug in TCS's implementation of BEMF, but it is a non-issue because you can either turn BEMF off (CV61=0), or better still configure BEMF to be only on from speed steps 1-12 (CV61=1 & CV10=12). Problem cured but you still have ultra smooth BEMF at low speeds, startup, and stopping.

    MM141/181 locos never had independent control of the headlamp. It is on at the same time as the fwd white running lights and therefore does not have its own function. F0 turns all lights on or off on 141/181, and they change direction automatically. The switches are for DC operation or consists. With DCC on 141/181 you wont need to change the switches. However the 071/201 do have separate functions for the head lamp, and cab lights (F0=directional running lights, F4=head lamp, F8=cab lights). So you can't turn the head light off on an MM141/181 entering a station unless you also turn off the running lights.
    Last edited by Noel; 11-01-2017 at 08:16 AM.

  3. #13
    Senior Member DiveController's Avatar
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    Thanks, Noel. That makes perfect sense. I was't aware of the problem with the TCS decoders but the 'fix' seems to be an excellent workaround. Needs to file that away in case I run with a bunch of Lais decoders. I had forgotten that the headlights were not independent on the 141/181s as have been messing about with a bunch of other things lately. A running session required obviously. Many thanks
    "Where Seventeen Railroads Meet the Sea"

  4. #14
    Quote Originally Posted by DiveController View Post
    Thanks, Noel. That makes perfect sense. I was't aware of the problem with the TCS decoders but the 'fix' seems to be an excellent workaround. Needs to file that away in case I run with a bunch of Lais decoders. I had forgotten that the headlights were not independent on the 141/181s as have been messing about with a bunch of other things lately. A running session required obviously. Many thanks
    Just be aware that the problem is only in the TCS decoder M4 ( which i think has been superseded anyway ). Mysteriously , the same bug appears in the LaisDCC decoder, no explanation advanced . There are a few different other far east decoders around as well

  5. #15
    Well I'm a happy bunny, they performed so well the Laisdcc will be my 'go to' decoder for non-sound MM Locos.

    Next step is to try the wired versions with a stay-alive capacitor in some of my steam model locos, especially 0-6-0s like my favourite GWR Pannier tanks.

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