I have a new Athearn SD-40 locomotive that I fitted with a Digitrax DH 123 decoder. I am using Digitrax power and throttles. I have not run this locomotive in DC.
My question is regarding the throttle amount needed to move the locomotive; it needs to be about 1/3 of full power before the locomotive will even begin to move. Meanwhile my other locomotive moves instantly on the application of minor throttle.
Do you know the reason for the SD-40 only moving on > 1/3 of full power? I am sure the answer is rather obvious.
Thanks for any help you can offer. I would like to run both as a consist.
Assuming it is just a new and tight drive mechanism, and not something rather poorly machined or fitted and causing inordinate friction in the drive or axles, each locomotive is to be treated as a unit in terms of providing the requisite and sufficient start voltage.
The fix is going to come in CV2, which we also call 'V-Start". You dial in a single speed step, or 1 on the throttle, and then enter programming. Make sure to select the correct mode for the engine's circumstances...alone or with other decodered engines on the powered tracks.
Once in programming, select CV2 and input a value near 10 to see what happens. If nothing happens, try 20. Still no movement, try 40. It would be unusual to not have some creeping of the engine with that value in CV2. Unusual, but not impossible. I have a Proto 2000 switcher that is upwards of 43.
If the engine moves off smartly, exit programming and dial down the throttle to 0. When the engine stops, enter programming and try a value of 30 this time. You'll have to exit immediately, dial in the speed step 1 again, and see what happens. If it refuses to budge again, try a value of 35, and you are going to be within two points either way by then.
-Crandell
I would do a reset of the decoder first. I installed a new Digitrax in an Atlas GP38 and on the first click of my throttle my train went from 0 to Mach 3. I dont know if that will fix your problem but it will least give you a clean slate when you start changing CV's
O to Mach 3 issue is usually a CV29 DC mode setting issue. Switch DC mode to off.
Springfield PA
Many thanks for the help. I reset the decoder. I then needed to set CV2 = ~ 45 in order to obtain motion (with throttle setting = 1).
I did find CV2 was rather "all or none" as the Athearn does not creep like my Atlas. If I go lower than 45 I find myself needing to increase the throttle to ~ 8 - 10 in order to obtain motion.
Your input certainly helped. I think I am in need of track/wheel cleaning in order to fine tune CV2.
When you had CV2 lower were you able to lower the throttle setting a bit after the loco started moving and have it still move? If so you may need to add some 'Kick Start'. Increase CV65 slightly, say 2 or 3.
From Digitrax Knowledge Base:
CV65 - Kick Start CV65 is the value of a brief pulse of power sent to the motor to get it moving. This is intended for use with a motor that takes a lot of power to get started but much less power to keep running. It can also be used to overcome some of the inertia in the mechanism of a locomotive. This is not the same as Vstart. Vstart is a continuous power level for the first speed step. Kick start is a pulse of power to nudge the loco into movement.
LivehaplingMany thanks for the help. I reset the decoder. I then needed to set CV2 = ~ 45 in order to obtain motion (with throttle setting = 1). I did find CV2 was rather "all or none" as the Athearn does not creep like my Atlas. If I go lower than 45 I find myself needing to increase the throttle to ~ 8 - 10 in order to obtain motion. Your input certainly helped. I think I am in need of track/wheel cleaning in order to fine tune CV2.
Good Luck but remember the CV29 setting. If the loco took off before it will probably do so again, at the worse possible moment.