Well,the mechanics and wiring I can do but programming is definitely my weakness.OK,here it is…the loco is an N scale Intermountain 4-8-8-2 Cabforward,the decoder a TCS DP2X P&P decoder,my easiest install ever.
I reprogrammed the adress as per Digitrax (DCS-200/DT400R setup) instructions,went fine but that’s about the extent of my programmer’s skills.Engine goes back and forth,all lights work great and this engine creeps fantastic,even moves (slower than this is stopped) at 1% throttle setting.I can’t ask for better.
My only problem is that all the speed this engine can achieve is obtained below 45% throttle,turning the knob further doesn’t create any noticeable change in the engine speed.Given this engine was no greyhound on DC, but I feel it could be slightly faster although it is about what I’d call “scale speed”, so I could live with this just fine.What I’d like is to have it’s maximum speed range spread over my throttle’s 100%.
Decoder is set at 128 steps BTW.Instruction sheet says that CV2,CV6 and CV5 should be given values to set start,mid and top volts respectively.Since the default values seem somewhat off for this particular engine,new values are required.My problem…I have no idea about these values,and don’t want to scramble an otherwise fine working decoder.I’m learning these things bits at a time but now my priority is on building my layout and I’d like to have this engine at the club’s show next month.
With nothing changed at all fromt he defaults, CV2, 6, and 5 give the maximum speed the deocder can provide.
There have been some locos where for whatever reaosn, BEMF limits the top speed, so you may want to adjust CV10 which is the BEMF cut-out. By default it never turns off BEMF, but by adjusting this you can have BEMF cut off above a certain speed. So you get that great creeping slow speed, but no hinderance on the top end.
But before you do that. - Set CV8=2 to do a complete reset of the decoder. Then reprogram the address - JUST the address. Just to make sure there aren’t any extraneous values in any of the other CVs that could be causing issues. If the top end is still slow, start playign with CV10. Values for CV10 are 0-128, corresponding to the speed step you want BEMF to cut out (0 means never). So if you want BEMF to stop at mid throttle, set CV10=64. Don;t worry, you can;t wreck anythign, and if you get hopelessly lost, just do the CV8=2 to reset the decoder back to factory defaults and start over.
I believe that that loco is geared slow to start with. Like my HO scale steam switchers they reach top end at or before half throttle. On a few of them I put a speed curve in to compensate a little and give better slow speed. Adjusting CV10 like Randy has suggested will help but I am afraid you will have to do a custom speed curve to go near 100 percent throttle. Even with that the slow speed curve will last too long. You will find that the loco is still moving at switching speeds at 10 to 15 percent throttle.
Thanks for both your inputs.Indeed this is no jack rabbit loco to start with but it’s top speed is what I’d call “visually scale” speed and since I’ll have a rather small layout for this type of engines,having some that handle slow speed nicely only make the layout this much larger.
I tried Randy’s trick and as he anticipated it didn’t change anything noticeable but as he had also said,it didn’t alter the loco’s great slow speed qualities,so I’m very happy.May be some day that I have a lot of spare time,I’ll tweak with CV10 more and see,but for now I’m testing my locos for the club’s weekend show in October as a priority.
I’ve had an Athearn Challenger (N scale) for two years now (pre-owned,bought on Ebay) that had never run on DCC although it ran nice on my DC test track.I finally took the bull by the horns and successfully corrected the problem.With both Digitrax and Athearn documentation (and some patience) I succeeded.There was some goof up somewhere in the CV’s.Don’t ask me wich CV was at fault,I simply rewrote all the CV’s that had something to do with adress,traction,etc and it revived,just like that.I’ve learned a bit more on DCC today by myself…come to think of it…quite proud of that!Thanks for the help,I may need it again,until I learn more…
BEMF is Back Electro-Motive Force. In simple terms, it is a way ot keeping a locomotive’s motor running at the same speed whether going uphill or downhill. BEMF can be adjusted or even turned off by changing CV values, depending on the brand of decoder you’re using.
For your TCS DP2X, you can go to the TCS web site and download their “Plain English Programming Guide,” which applies to all TCS decoders.
Unless your TCS decoder is one of the most recent releases, it does not have BEMF and there is a separate document on the TCS web site explaining how to adjust their new BEMF-capable decoders.
TCS decoders have all had BEMF for several years now. 5 at least.
The basic instructions that come with the decoders are enough to get started, but there are far more adjustments thne listed there. The BEMF manual has the details on all the BEMF settings, and there is also an extra function guide which lists more details on configuring lighting effects - there are are LOT of tweaks you cna do to get just the right effect. JMRI can also help, if you need to go beyond what’s on the basic quick start sheet that comes with the decoders.
I would try reading back CV 5 and CV 6, the max and mid-range speed settings. I suspect maybe the same number got programmed into both. For a “straight line” curve (where the engine gets progressively faster by the same amount as you turn the throttle up) CV 6 (midrange) should be half of what CV 5 (maximum speed) is.
Well, since the issue is that it doesn;t go any faster past 45% throttle setting CV5 and 6 to 0 would mean straight line curve, no limitation on the top speed. If the loco was too fast, setting CV5 to something less than 255 would reduce said top speed, but if CV5 is already 0, that is the typical default for most decoders and means provide maximum voltage at the top end. I would suggest verifying that CV5 and 6 are both 0, because if they were inadvertantly set, or if they happen to be stuck with non-zero values from factory testing, it could be reducing the speed. If the top speed is too slow, and CV5 is already 0, making it 255 won’t change anything, for any decoder that uses 0 as a default, which TCS does. Some decoders also choke if CV5 is less than CV6 - mid shoudl eb lower than top, it doesn’t make sense the other way, but nothign prevents you from programmign it that way. It’s been known to cause odd problems.