# Are there "un-readable" decoders?



## Brakeman Jake (Mar 8, 2009)

I have two brand new Kato locos awaiting Tsunami instals that I wanted to test their vital signs before the transplant.They ran fine on DC but I also wanted to try them on DCC just for the fun of it.So I fitted a DH123D with an eight pin plug and then on the programing track.

Dial in a ficticious adress,set a linear speed curve...then on the test track.Loco won't start moving before twenty some clicks...so back on prog. track,reset start voltage and speed curve...results in a much better response though still short of perfection.Conclusion,the decoder accepts the datas and works at least decent.

Curiously though,when I try to read back the CV's (with Decoder Pro/PR3/PTB100),I get the "no aknowledge from loco"...???Is it my setup or are there decoders that simply can't be read?I know it's a cheap one so it makes sense to me.Could this be?


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## waltr (Aug 15, 2011)

Read back turns on the motor to pulse a current through the track. If the motor draws too little current then it won't read back (my theory). 
Try connecting a 100 Ohm resistor across the programming track. This will increase the current draw and may now read back.

I've used and can read back a DH123D decoder so it shouldn't be the decoder.
Then let us know if this worked. In the mean time maybe someone else will jump in here.


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## Brakeman Jake (Mar 8, 2009)

Question answered...thanks.I had re-written a few CV's while it was on the loco using Decoder Pro and it's only after removing it from the loco that I tried to read it through a decoder tester that doesn't put any motor load on it.So it makes plenty of sense.


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## NIMT (Jan 6, 2011)

Old MRC's do not support readback and they can be very "flying by the seat of your pants" programming.
Glad you figured it out!:thumbsup::thumbsup:


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