Digitrax Decoders Inst in MT SW1500 & ATL MP15DC & Nothing Happening

[tehachapifan]

I am brand spankin' new to DCC and just installed a MRC Prodigy Express 2 DCC system on my layout ant tested it with the Bachmann 44 tonner. It works! I then installed the Digitrax MT SW1500 decoder in my, well, MT SW1500 and I can't get anything to happen. Tried address 0003 but that did not seem to work (although the Digitrax manual mentioned default is 03...is that the same?) So far, I can only program on the main and I tried to reprogram the address to 0322 to match the road number. Might've screwed something up even more in the process. The only sign of life is a brief power up when I put the loco on the track. Sigh...

....I should mention that the loco shell is back on and all contacts are contacted. For all I know, the MRC system I purchased is not compatible with the decoder.

[Philip H]

All current decoders are generally comparable with all systems - you can thank the NMRA for that one. With this new decoder I don't know if there's an upside or or not to this one, but the six pin decoders for FVM and similar can be installed upside down. So take unit apart again and see.

[tehachapifan]

Thanks but this one can only go in one way. Contacts are good and tight in the frame too.

I seem to be getting lights, which will go on and off on command, but I still get zero movement.

[peteski]

If you can select the decoder's address and control the headlights that would imply that the decoder is properly connected to the track and it is seeing the DCC signal.  Make sure that the motor leads are properly connected to the decoder.

Also, did you check if the loco worked in DC before you installed the decoder?  Maybe the loco was defective to begin with?

[tehachapifan]

Yes, the loco worked in DC just fine and I checked the motor lead connections several times. The wires are firmly seated in the provided plugs. I decided to take a break from this loco and try to install the Digitrax decoder in my Atlas MP15DC. Interestingly, I'm getting the exact same behavior (lights but no movement). I've tried to adjust the motor contacts to make contact with the provided pads on the decoder, but that is a completely blind operation and no way to tell if it's making proper contact. The 44 tonner still works fine. Really hoping that the MRC system is somehow not talking to the decoders properly but is resolvable (I may have committed a programming error). Beginning to worry that going to DCC may have added a level of frustration I didn't need.

....also, the MP15DC decoder came tightly bound up in Kapton tape at one end. Didn't see anything about it in the instructions (and the pictures showed it without the tape around it), so I removed it. Hope that was correct.

[peteski]

Without the ability to read back the decoder's CV register values I would find any DCC system frustrating (as you are pretty much blind when trying to troubleshooting).

For example default value for CV 29 is 6. That enables 28/128 speed steps mode and analog operation.  The last option means that you can run that loco on DC and it should work.  Assuming that the CV 29 retains its default value of 6 (you can't really verify that now).  try to run it on DC. If you have an old-fashion DC throttle which supplies pulsed DC (which can confuse the decoder), then just try running the loco using a 9V battery.  If it runs then the motor driver on the decoder is at least working properly and the motor is properly connected.

[nkalanaga]

If you take the decoder out does it still run on DC?

[tehachapifan]

Thanks, Peteski! I actually got the MP15DC running. I took it apart again, re-tweaked the motor contacts and now it works great. SW1500 is still a no-go. I'll give your suggestions a try on that one.

[tehachapifan]

...OK, switched the layout to analog and the SW1500 only runs in reverse (in a strange, lunging way). No forward lights or movement in analog, forward lights only in DCC but no movement. Rechecked the motor contacts yet again. I would have to guess bad decoder.

[peteski]

...OK, switched the layout to analog and the SW1500 only runs in reverse (in a strange, lunging way). No forward lights or movement in analog, forward lights only in DCC but no movement. Rechecked the motor contacts yet again. I would have to guess bad decoder.

Yes, the decoder could be bad. But before condemning it make sure that there are no shorts between the frame halves and the motor leads. That could possibly make the model behave strangely.

If you have an ohmmeter or a continuity tester, touch one lead to one of the motor leads plugged into the decoder and then touch the other meter lead to each of the frame halves.  There should be no continuity (or very high resistance) between either frame half and the motor lead. Then repeat the test but on the other motor lead.

[tehachapifan]

Thanks, Peteski, but you are now 2 or 3 steps above my (thick) head and I don't have the equimpment you mention. I did try to start fresh this AM and reinstalled the DC board. Loco ran fine forward but poorly in reverse for some reason. This was with the shell off but the sill on (maybe not enough weight?). Then I reinstalled the DCC board and tried that with the sill on. Nothing at first, did some motor lead wire wiggling and have some sporadic signs of life. Then the loco started making the strangest noise I've heard a loco make (sort of an electronic tone-type noise) followed by a trail of smoke out of the decoder. Color me down as pretty darn frustrated. Thankfully, the MP15DC (Actually, my MP15AC bash) and 44 Tonner are still working well on DCC.

[Philip H]

Well, now hat the decoder is toast (sorry) it would seem you have a definite short somewhere. You should be able to get a new decoder under warranty. While you are waiting for that I'd start tracing electrical pathways in the clock however you can.

[peteski]

Model Railroading is a multifaceted hobby (one of the reasons I like it).  You have to be willing to be a painter, sculptor, carpenter, mechanical engineer and an electrician.  Otherwise the hobby will frustrate you.

IMO, even without using DCC, any budding model railroader should have an inexpensive multimeter and have some basic understanding of electricity.  Things like open, short or continuity should be terms you have an inkling about.  Even in DC modeling you will eventually encounter some problem which will require some basic electrical troubleshooting.

[tehachapifan]

Had a drafted another reply by decided to stop posting on the subject. Feel like I'm coming across as bashing these products (which I'm not) or might inadvertently scare someone away from giving it a try. Gonna chalk it up to my own lack of skills and bad luck. Thanks for the help, guys!

[Philip H]

Digitrax has a no worries warranty as long as you initiate the replacement through their website. Just go fill out the web form, print the copy at the end and send it in.

As to the other, while I agree with Peteski about owning a multimeter and knowing some electricity terms and theory, the reality is this stuff is mostly supposed to be plug and play. So if a short we're caused by a missing piece dot laptop tape that should have been factory installed, then you can try a decoder without knowing it. All peteski was doing was walking you through the test procedure. Having so done else do your installs certainly solves the problem for you, but its not always as satisfying as diagnosing and solving the problems yourself.