Locos That Run On DCC Only ???

[kornellred]

I have an N Scale Atlas C420 and an N Scale Atlas U23B that I picked up on eBay a few years ago.  They both have sound decoders (do not know the brand as I have never removed the shells to look) and both units run nicely and the sound is generally poor and very low volume. (I have significant hearing loss so the sound quality may be "just me")

Neither of the units respond to DC at all.  I changed CV 8 to 8 to do a factory reset.  Still no response to DC voltage.  The loco addresses did revert to 3.  AFAIK, NMRA standards require DCC-equipped locos to be operable on analog DC.  I am aware that starting DC voltages for sound decoders is much higher than non-sound decoders, and I have applied up to 13 VDC to these units and still no response.

Has anyone ever heard of a situation like this?  Thanks in advance.

[Sumner]

First thing I'd do is to read CV 29 and see what the value is there and see if DC is turned on or off.

http://www.2mm.org.uk/articles/cv29%20calculator.htm

Read what is there and put the number in the calculator above and use the 'BackCalc' button and you can see if DC is on or off.

Sumner

[wvgca]

CV29 normally holds the DCC and/or DC info .... a normal reset CV8=8 does not change that value ...
read CV29 and see what it is

[peteski]

Yes, if you have the ability to read the CVs from those decoders (I assume that you do since you did the CV8 reset), then read and decode the settings in CV29.

I'm also surprised that the alternate power source (what we colloquially call "DC mode") bit in CV29 would not be set. Most decoders have that bit set to enable DC operation. If that "alternate power source" bit is set (bit 2), also  check if CV12 is set to "1".

See https://dccwiki-prod1362-images.b-cdn.net/images/4/42/CV29-Oct-21.png

I also do not believe that either of the locos mentioned came with a factory installed sound decoder, so those are probably aftermarket installs.  I could be wrong though.