I think I read about this before, but what causes a DCC locomotive to "run" fast on the track when the power is first applied, even on the wrong CV number? I have 4 Athearn blue box with Soundtraxx decoders with the same CV (for consist) that all take off fast when first set on the track. I checked a different locomotive and it was fine at the correct CV, otherwise it just sat still. These other 4 locos were working just fine awhiile back. I'm stumped. Is there vodoo in the air??
Modern decoders for about 16+ years have been 'dual mode', meaning they'll run on either DC or digital track power. That function must be enabled in CV29.
When some decoders sense a high inrush of current from the track when you apply DCC power, they get tricked into suspecting it's really DC current. However, they don't get that slowly increasing power as one would dial it up in DC. It gets the full 14 volt track power that always-full DCC power is to the rails. Naturally, at all those volts, it takes off like a scared cat.
If any of yours do this, go into CV29 and assign it a value of '34'. That kills the dual mode capability and will only allow the decoder to wait for DCC current.
JRPThese other 4 locos were working just fine awhiile back. I'm stumped. Is there vodoo in the air??
Do you use more than one throttle? Depending on what command station you use you may have the same address on another throttle and the speed setting is not at zero.
Perhaps.
Good Luck, Ed
Checked all 4 locos and CV29 is already set to 34. They still take off when I hit the power button (throttle). Even changing the CV number that is normally assigned to the loco and it still takes off. Wierd that all 4 loco's do this as they have separate decoders in each of them. The CV information for all of my locomotives is located on JMRI.
Check Ed's suggestion earlier, but maybe the best thing to do would be to simply reset all the decoders. Make sure you do the reset appropriate for the decoder...don't rely on CV8 set to a value of "08".
Yes, good idea. Having JMRI makes it easy. Will send you all an update when completed. Thanks.
JRP
I'm not sure all the different brands of decoders use the same CV setting to turn off DC/dual mode? In any case, in JMRI Decoder Pro, I think it's a simple on/off setting you can adjust with one click.
All, I reset all of the decoders on JMRI and they are all running fine now. Thanks for the great tips and response. Have a wonderful Thanksgiving and please stay safe. We need more model railroaders in the world today.
On Soundtraxx decoders, it is a combination of CV29, bit2 and CV12, bit0 to resolve this potential run off issue.
Marc
wjstix I'm not sure all the different brands of decoders use the same CV setting to turn off DC/dual mode? In any case, in JMRI Decoder Pro, I think it's a simple on/off setting you can adjust with one click.
CV29 is a required CV per the NMRA standards. Not even optional. Note that the SOundtraxx documentation says bit 2 of CV29 must be set for CV12 to have any effect.(manual actually says bit 3 of CV29 - that's wrong, it's bit 2) I suspect CV12 is there for possible future fetures for the decoders to run on AC or maybe Marklin MFX protocol.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.