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Fine tuning Digitrax DH123AT decoder Track and electrical/DCC
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Active Member 34 posts Thommo Active Member 34 posts
Thommo

Hello all!

I have installed DH123AT decoder in the HO Bachmann Shay loco. No problems there, I used 8-pin harness for the decoder.

But, as I use it, I noticed that decoder works in a strange manner. When I turn the control knob to FORW or REVERSE, loco starts a bit fast, like a little power surge is applied to the motor, and than goes smoothly through whole speed range, and also deccelerates with no surges.

It seams the problem is only in the moment between idle and go points in time.

I hope you will understand what is my problem. Anybody has some idea?

Thanks!

The Railway Enthusiasts Society "Stacion", Rijeka - Croatia • http://www.stacion.hr
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JaySmith Regular poster 174 posts
JaySmith

 How many speed steps you

How many speed steps you using?

Jay Smith

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Thommo Active Member 34 posts
Thommo

I have tried 28 and 128. Same

I have tried 28 and 128. Same stuff.

Dont get me wrong: It is not so big deal, but it is a little irritating. I hope modifying some CV's can remove this "surge". Can the "dither" be responsible?

The Railway Enthusiasts Society "Stacion", Rijeka - Croatia • http://www.stacion.hr
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jeffshultz MRH Staff 7,992 posts
jeffshultz

Do you have access to Decoder Pro?

It would be interesting to see what your motor and speed control settings are.

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Jeff Shultz - MRH Technical Assistant
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joef MRH Founder 17,525 posts
joef

What's your kick start CV value?

What value do you have in CV 65 - Kick start voltage? If its a large number, this could be your issue ... Also, what's CV2 - start voltage? Make the value smaller and see if that helps.

Next, it could be the mechanism has some stiffness and it smooths out once the motor is finally turning. To alleviate this, increase the value of CV 3 - Acceleration, to mask this tendency.

If it turns out the motor is stiff, installing a decoder with Back EMF can help. I'm particularly fond of TCS decoders these days - they almost all have BEMF, and their lighting effects are superb.

Joe Fugate​
Publisher, Model Railroad Hobbyist magazine

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Thommo Active Member 34 posts
Thommo

Joe, my friend and I did put

Joe, my friend and I did put CV65 to zero, even before I loged on to this thread, and Shay is now running without surge.

 

Jeff, I was experimenting with this Digitrax decoder settings for the Shay, and this is what suits me:
CV2=4, CV5=16, CV6=10, CV3=24, CV4=32, CV65=0.

I think this decoder is a keeper in Shay, but if I stumble on some extra cash some day, it can be replaced by Soundtraxx light logger...

 

I have TCS M1 in one of my european electrics, it is a superb decoder! I plan to buy few more.

Thank you all.

The Railway Enthusiasts Society "Stacion", Rijeka - Croatia • http://www.stacion.hr
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