Engine Buzz/Hum with DCC

Discussion in 'DCC & Electronics' started by NH 2525, Jan 12, 2006.

  1. NH 2525

    NH 2525 New Member

    Hi. I'm relatively new to DCC. I had purchased a number of Atlas decoder equipped locomotives, including the Trainmaster, B 23-7's, SD 35's, and a U25B. These ran very quietly on regular DC power, but now that I've switched over to DCC, there is a loud buzz or hum from the motors when starting the loco, or when moving at really slow speeds. I have a LENZ SET 100, with the recommended DIgitrax power supply. Is there anything I can do to get rid of that noise. All of the factory DCC equipped locomotives do this,despite the fact that they were relatively silent and smooth operators on straight DC.

    I have switched between the various speed steps and this has not helped.

    Edit: I should add that these are N scale locomotives.

  2. MasonJar

    MasonJar It's not rocket surgery

    Hi NH,

    Welcome to The Gauge.

    I don't have a complete answer for you, but generally "yes". There are CV's that can help you fine tune the frequencies that cause the buzzing. I do not have my (Digitrax) manual in front of me, so I can't tell you which ones (besides, that info may only apply to the Digitrax decoder I have). Other CVs like starting voltage and so on may play a factor.

    What does the Atlas manual say about this? Is it in their "troubleshooting" section?

  3. NH 2525

    NH 2525 New Member

    I'll have to download those manuals from the Atlas site. Unfortunately, there is no manual provided with decoder equipped locomotives. I installed two Digitrax DN 163A0 decoders in SD35's. These run nice and quiet.

    Thanks for the Atlas manual suggestion. I have not attempeted to program any CV's yet. I am still confused about that. I just need take some time and read up on that process.

    Thanks again.
  4. rksstl

    rksstl Member

  5. NH 2525

    NH 2525 New Member

    Thanks Rich. The manual is helpful and I actually have that one from the package with the decoders I purchased. The digitrax decoders that I installed provided fairly quiet operation. It is the Factory installed LENZ decoders from Atlas that are giving me noisy operation. I'll have to download those fromthe Atlas site. I just can't figure out which CV's do what and how to write new values to them.

    I have also learned that I'm sticking with doing my own decoder installations from now on. I couldn't believe how easy it is.

  6. DWP

    DWP Member

    The sound you describe is the same sound I get when I put a DC, no decoder, loco on
    a DCC track. If you have a DC only loco put it on the track and see if it sounds the same.
    Do the loco's have the factory decoder in side and is it hooked UP?

  7. NH 2525

    NH 2525 New Member

    Thanks. The sound is very different from a straight DC locomotive operating on DCC track. This is an distinct electrical buzz or humming sound. It does not sound like a DC loco's whining, which has a much higher pitched tone when on a DCC powered track. Again, this deeper sounding buzz is happening with all 12 of the various Atlas factory decoder equipped locomotives. I do not get this sound with the two Atlas SD-35's I installed the Digitrax DN163A0 decoders into on my own. All of the factory decoder units had been run on DC power, prior to my switch to DCC. They were silent then, but not now.

    Thanks again for all of the help and suggestions. It is hard to describe the sound. It is really like the sound of an electric motor struggling to start up. It is a deep sounding buzz. It disappears as the loco picks up speed, but is there constant when running at slower prototypical speeds.
  8. Gary Pfeil

    Gary Pfeil Active Member

    I haven't read all the posts so may repeat something here, sorry. At least some of the Atlas locos which come with decoders have a jumper plug installed, and come set up to run on DC. To run on DCC, you are supposed to move the plug to a different position. I don't recall if it needs to be flipped around 180 degrees, or moved over one set of contacts. I would assume that if you try to run the loco as it comes on DCC, it would exhibit the same characteristics as a straight DC loco, which is to sing. And the volume, or pitch, of that singing would decrease as you open the throttle. Check your instructions, if you have them, it should show where the jumper is located, mine was under the dynamic brake grid.

    If this is your problem, you'll notice the loco won't run thru a reverse block set up with a reverse module, because it is still in analog mode.

    I just read thru the posts and was going to delete this but figured I'd leave it anyway. I hadn't noticed your comment on N scale and I was talking HO. Also, you mention it sounds different than analog. I don't know if the N scale locos have the jumper I mention. Do your Atlas locos go thru DCC reverse blocks ok?
  9. NH 2525

    NH 2525 New Member


    Thanks for the reply. There is no jumper on these n scale decoders, but there is a CV that allows for dual operation mode DC/DCC or DCC only. I'll have to check those settings when I figure out what I'm doing with CV's. I'm still on the steep upslope of that learning curve.

Share This Page