Why do some motors run improperly on DCC?

[CentralMaryland]

Hey, there. I've had trouble with some of my locomotive's motors functioning poorly Digitrax DCC system. After installing the decoders, two of my engines run at a quarter of the speed they should run. One motor is a 1970's vintage "tan can", while the other appears similar yet has no name on it. All my other engines run fine. If anyone knows a recourse to fix this besides simply replacing the motors, or, failing that, at least know why this problem occurs.

Thankya much!

- Wink, Central Maryland Model Railroad

[Stourbridge Lion]

CentralMaryland - Welcome to trains.com!

[rrinker]

 What decoders did you put in? Hav eyou tried resettign said decoders to factory defaults? If you've accidently set CV5 to a non-zero value, you could eb limiting the top speed. If they are a decoder that offers a 'switching speed' option like Digitrax and a few others, this could be engaged, which cuts the speed in half. If there's a wiring error you could be getting an intermittant short which will cuase erratic operation until it finally blows the decoder. There are many variables here, especially since your other locos run fine - there's somethign up with these two or their decoders.

                                  --Randy

 

[wjstix]

If the engines ran fine on DC, they should run fine on DCC assuming you installed the decoder correctly, and the settings (CV's) are correct.

Since you're dealing with a 1970's engine, did you isolate the motor from the engine frame??

Until maybe the 1990's, engines often had one lead for the motor connected directly to the engine frame. You have to insulate the motor from the frame when installing a decoder. On older steam engines, that often just means removing the motor (often held in place with one screw), putting down tape or some other thin insulating material, and reconnecting the motor mount with a plastic screw replacing the metal one.