# DCC issue



## 93firebird (Dec 25, 2011)

I recently upgraded my DCC unit from the Bachmann easy command to the Digitrax zephyr extra. All of my locos are running, however, one of my mainline locos is not running up to speed. I have tried cleaning the track, and adjusting the cv values relative to speed, but the unit just does not run as fast as it should. The loco is a Bachmann spectrum 2-10-2, with a digitrax decoder sdh164d. It ran fine using the Bachmann setup. Any suggestions would be helpful.
Thanks


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## NIMT (Jan 6, 2011)

What value do you have in CV 29?


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## 93firebird (Dec 25, 2011)

I have it set default 6


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## NIMT (Jan 6, 2011)

AH HA 
What is the Cab # that you want to use?


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## 93firebird (Dec 25, 2011)

NIMT said:


> AH HA
> What is the Cab # that you want to use?


Cab #??? Not sure what you mean by that


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## NIMT (Jan 6, 2011)

Sorry, Engine # like 6 or old #99 or 2699?
Also called the decoder address#.


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## 93firebird (Dec 25, 2011)

That's what I thought you meant but wanted to be sure. The loco in question is set to 1


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## NIMT (Jan 6, 2011)

OK there are 2 ways to go about setting them up:
You can use the Basic Speed Control:
_CV1=1, CV2=0, CV5=255, CV6=127, CV29=6_
Or a better path would be to Set up the Speed Table.
_CV1=1, CV29=22, CV67=1, CV68=10, CV69=19, CV70=29, CV71=38, CV72=47, CV73=57, CV74=66, CV75=75, CV76=85, CV77=94, CV78=104, CV79=113, CV80=122, CV81=132, CV82=141, CV83=150, CV84=160, CV85=169, CV86=179, CV87=188, CV88=197, CV89=207, CV90=216, CV91=225, CV92=235, CV93=244, CV94=254_


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## 93firebird (Dec 25, 2011)

Tried option 2, did not resolve the issue! What's next?


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## Brakeman Jake (Mar 8, 2009)

Just my two cents...pretty much looks like a problem I've experienced lately.Could there be some BEMF involved in this?What do you think Sean?


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## NIMT (Jan 6, 2011)

Jake,
You possibly could be right.
93firebird, 
What value is in CV57?


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## 93firebird (Dec 25, 2011)

Just wondering how anything could change from one system to the next. I simply changed controller.


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## 93firebird (Dec 25, 2011)

Cv 57 is set at 6


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## Brakeman Jake (Mar 8, 2009)

You are,just like me,starting to learn about DCC.This technology opens a whole world of possibilities for controlling model trains but does have a learning process along the way.Once you'll understand how it works,wich isn't as hard as it may seem at first,you'll enjoy it and won't want to go back.

OK...only my theory here,Sean will tell you more.He's worked with me on a similarly looking problem I had two weeks ago with two identical brand new loco/decoder setups.It was found that,in my case,a function called BEMF was limiting the top speed of the locos.Speed range was limited to about 50% throttle,no more acceleration behond that.Turning it off by setting CV61 to 0 corrected the problem.

I'll leave to Sean to explain how BEMF works and what it does to the loco.However,I've been explained on another forum that my TCS decoders have self adjusting BEMF and that it used track voltage as a reference to adjust itself.Since they are originally designed for HO voltage,my N scale locos ran poorly on N scale voltage setting,wich is an only Digitrax feature.When I tried HO setting (higher voltage) they ran fine.For these to run OK on N scale setting,BEMF will have to be readjusted,I've turned it off for the moment.

Still a theory...if your loco ran fine with your Bachmann set,may be it is that the Bachmann set pushes a little higher voltage to the track wich is not necessarily a better thing.And your other locos run fine...may be they don't have BEMF feature.Now let's read what Sean thinks of all this,I'm no pro yet,still learning............


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## NIMT (Jan 6, 2011)

BEMF is ON let's turn it off by setting CV57 to 0 and see if that helps.

Jake did a great job of explaining it, BEMF in simple terms is like cruise control for the trains, it compensates for the voltage that is being applied to the rails to keep all engines running smooth.
The reason for the difference became apparent when you switched systems is not because the Zephyr is putting less voltage or amperage to the rails as it would seam because it's running slower but because it's putting more to the rails and the decoder is compensating for that.


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## 93firebird (Dec 25, 2011)

Set 57 to 0, much improved but still not 100%, do I need to address 55 and 56 as well


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## NIMT (Jan 6, 2011)

You can set those to 0 too but the should just be off and disregarded.
I just noticed that I gave you the wrong # for CV94 go back in and check and make sure it's set to 255 not 254...Oops sorry!
Retest! How close is close? 
I don't have a Zephyr but on my DCS200 I can set the track voltage. Look in the manual or maybe someone with one can chime in.


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## 93firebird (Dec 25, 2011)

All is good now. 
Thanks for all the help it has been much appreciated.


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## NIMT (Jan 6, 2011)

What do it end up being?
Or what did you do to fix it?


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## Brakeman Jake (Mar 8, 2009)

Indeed,I'd love to read about it too.....thanks.


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