Testing A Drop-In Decoder With the NCE Tester

[BCR751]

I have a TCS AMD4 decoder I want to test with an NCE 5240219 decoder tester.  All I need to do is read the mfg. and decoder version to make sure the decoder is at least somewhat working.  If I connect the tester's TRACK connector to the programming track and the RED and BLACK wires from the tester to the pick-up pads on the decoder, will this work?

Doug

[peteski]

You need to also connect the gray/orange motor leads to add an electric load to the decoder.  The decoder needs that load to acknowledge programming packets from the command station.  Without that load the command station will likely net be able to read the CVs (the on-board LEDs might not be enough of an electric load).

[BCR751]

The NCE tester has an incandescent bulb that's supposed to provide a suitable load if there's no motor attached.  I just tried this out on one of the Lenz decoders from an Atlas C-630 And the tester came up with 'can not read CV's'  I think the decoder is fried.

Doug

[peteski]

The NCE tester has an incandescent bulb that's supposed to provide a suitable load if there's no motor attached.  I just tried this out on one of the Lenz decoders from an Atlas C-630 And the tester came up with 'can not read CV's'  I think the decoder is fried.

Doug

But is the bulb attached to the decoder in any way?  It has to be powered through the decoder.  Your initial statement seems to indicate that only red and black wires are connected from the decoder to the tester.  That does not connect any type of a load to the decoder.



I suspect that it uses the bulb to simulate a motor load and LEDs for function output indicators. But in order for the tester to work properly you need to connect the gray/orange wires from the tester to the decoder (to attach the bulb as a load for the decoder's motor outputs).  So as a bare minimum, the tester needs 4 wires attached to the decoder for the test to work: red. black, orange, gray.

[BCR751]

Sorry Pete.  I should have stated that I indeed did hook up the orange and gray wires to the motor pads on the decoder.  I ran it through the programming track, changed the long and sort addresses (someone had reversed them) and had all functions working.  However, when installed in a loco, I have nothing.  So, obviously something is haywire with the loco.  On to further checks.  Thanks for the input.

Doug

[peteski]

If after the failed install in the loco you took it out and it tested good on the tester then the most likely problem (with the loco) is that either the motor contacts are not contacting the decoder's pads, or the frame is not making good contact with the decoder. In my experience, both are common problems for this type of install.  I suppose that there could also have been a sort between the decoder and frame, but that is less common problem,  and it could fry the decoder.

[BCR751]

With the help of a fellow on the TCS forum, I was able to determine that somehow the 4-digit address function had been disabled so the system was not talking to the decoder when I used the loco cab number.  I reset the decoder and re-programmed it using the 4-digit address and now every thing works fine.  And, for future reference, the NCE tester does a fine job on the NCE decoder.  I also tried it on one of the Atlas/Lenz decoders and it worked there as well.

Doug

[peteski]

Thanks for the followup.  I'm glad that you resolved your problem, and that the decoder hardware was ok.

With non-responsive decoders the first thing to do is to try reading the CVs (on programming track).  That operation does not need an address, so the decoder should be readable (assuming that the decoder has enough of a load like a motor attached to be able to acknowledge the programming packets).  Pretty much any brand decoder should act this way.
Reading CV29 should give a clue as to what address and speed step mode the decoder is programmed to use. Then read either 2- or 4-digit address CVs.  Or just reset the decoder to factory defaults which will program it to short address of "3".  While that procedure might be slightly different between manufacturers, it usually involves writing some value to CV8.