DCC equipped locos run slower on DC

[cncproadwarrior]

I have two locos equipped with DCC decoders and they run noticeably slower with my non-DCC equipped locos on my DC layout. I'll be going to DCC eventually. One is a late 80s Athearn SD40-2 and the other is a newly purchased DCC equipped Atlas SD40-2. Is this normal?

 

[Selector]

I take it that these are not sound units? Sound units, for sure, won't turn a wheel until about 6 volts are getting to the decoder because the amplifier circuitry and the speaker require much of the first chunk delivered.

Otherwise, I wonder if the DCC units have different drivetrains that require more voltage to run. I can't think of anything else that would cause them to run noticeably slower, unless the gearing is substantially different on those models.

-Crandell

 

[cncproadwarrior]

Crandell,

The Atlas unit is new and sound equipped but I don't think there is a decoder in it now that I think of it. I haven't opened it up yet. DCC ready? It runs perfectly if alone on the track.

The Athearn unit is a late 80s model, DCC decoder equipped but not sound equipped and also runs fine solo.

 

[redwine_P]

My Bachmann DCC equipped run slower on DC than the straight DC loco`s do as well. I have a DC Athearn SD-45 Demonstarighter that will fly off the track it`s so fast if you dont watch how you run it.

 

[Selector]

Bernie, if the Atlas has sound, it must have a decoder.

It is a dual mode decoder if it operates on DC current, and it is typically the case that sound decoders suck up the 'cream' of the voltage first for the sake of making sounds. Only after you have physically dialled in 6+ volts will the decoder meter out voltage to the motor. In DCC systems, the track always receives about 16 volts, but it is a square wave AC current. The decoder gets more than it needs for what it must do, and that means it can begin to move the engine immediately using up the overage from 6 volts.

-Crandell

 

[diburning]

The decoder draws some power to run the on-board chip so it doesn't give the motor the full voltage.

Also, when you switch to DCC, you will find that you will have better control of your trains as on DC, the max you're giving the motor is about 12 volts, where on DCC, the decoder/system may give the motor 14-16 volts max.