I am running HO scale with a Digitrax Super Extra Chief and all my decoders are Digitrax. I noticed that some of my locomotives dont start until I reach around 60 on the control knob and when I reach 99 they are not moving that fast. There are a few Atlas and some Athearn RTR units that do this. I guess I am wondering why they are like this and how to change this so they start sooner on the speed knob. Thanks in advance.
Cv2 is the voltage given to the loco when you go to speed step 1. To set it, dial up the loco, run the loco for 20-30 minutes at med speed (to warm it up), turn the knob so the speed says 1, enter ops mode programming and input larger and larger values into cv2 until you see the loco start to creep. That way when you turn the knob, the loco responds right away. Athears usually require large values for cv2. However, if your loco is gummed up, then consider taking the trucks apart and ungunking the gears up. David B
David offers good advice. Many times a locomotive needs a good break in period to loosen it up and the performance improves. In some cases the gear grease has thickened an inhibits running. This can be a problem with a “new” loco that has been sitting on the hobby shop shelf for a long time. Check the values for CV2 (start voltage). This can be adjusted to that your loco will start at a lower throttle setting. Check CV5 (Top speed). It can be adjusted to give you a higher top speed at the high throttle setting. CV6 (mid range) is the setting for the middle range speed. These values will differ for each loco.
Joe
Changed CV2 to 50, works perfect, thank you.
CV2 of 50 is way way way to high! I never seen it go above 30 for an open frame motor. Today’s can motors can be as low as CV2 = 2 or 3!
Do you know what your track voltage is?
You can measure it using a standard volt meter. If you are running way too thin a wire over a long distance, the voltage to your train will drop drastically causing a much higher CV2 value necessary. 14.25 VDCC is the standard track voltage for HO.
I’ve seen athearns as high as 70 for cv2. Not way too high. Remember that the voltage needed to turn the motor is dependant on how much friction is in the drive line. Katos will have a smaller number than old Pittman powered locos. 50 is right in the ball park for an un-gunked Athearn. David B
I believe what you say David if you encountered this, but it’s quite surprising. I never encountered one over 30 myself. (40+ engines)
CV2 = 70 is ~4V give or take
Especially with modern decoders which usually implement start pwm and kick feature.
I agree with David, I have one Athearn RTR SD40-2 that needed CV2=70.
Wow, remind me to remotor an SD40-2 if I ever get my hands on one.
Wait is this the Athearn motors that sound like they come out of a vacuum cleaner? Didn’t they stop using those like 10 years ago? (I learned something new today)
Consider also it’s probably a DH123, with no BEMF.
Most of my locos start and run on step 1 or 2 without setting CV2, but I use only BEMF decoders from TCS. Even the Athearn one, although it is a newer RTR RS3, not an old Blue Box type.
–Randy
It isn’t only the motor, it is everything it has to turn. If you remove the trucks from a kato sd40-2 and the trucks from an Athearn sd40-2 and compared their “free-rolling-ness”, you will see how much less friction is in the kato driveline. The Athearn gears haven’t changes since they got rid of rubber band drives. To free up athearn’s trucks, you need to dissasemble them, clean all the grease off, introduce some sort of polishing agent, run the gears to polish them, clean them, lube them and reassemble. The Athearn motor will run with less voltage if you cut the brush springs and clean and treat the commutator with a conductive promoter. Hope this helps. David B
It is a DH123PS, I didnt thing that 50 was too high. I talked to several others who were in that area for Athearn RTR units. All the gears are clean, no gum on any. Thanks for the info.
Track bus is 12GA, feeder wires are 18GA. longest bus is 22’, longest feeder is 12"