Newbie question about "drop-in" decoder

[gbcaboose]

I run straight DC, but decided to install a few Digitrax decoders in a few of my locomotives to run them on my club's DCC N-Track layout.

I installed 3 Digitrax DN163A4's into 3 Atlas DCC ready GP30's. Installation was smooth and easy with no apparent problems. However, now they won't run on my test track, which is powered by an MRC Tech II 1440. No movement, no lights, no nothing. If I rock them side to side with the throttle on the lights will flicker some (both front and rear at the same time). All the GP30's ran fine before the installation.

Also of note, I purchased 2 DCC GP40-2's from Dave Foxx's N-scale emporium. These 2 locomotives will run on the test track, but not smoothly. They speed is pulsed and it's uniform. Faster - slower-faster-slower all the way down the track. This makes me think it's a throttle issue. But why do the GP30's not move at all? Do they need to be programed to run on a DC track? I thought the default setting was to run on both DC and DCC. It will be another month before I can make it to another club "run night" and put them on a programming track.

Any help or words of advice would be appreciated.

Thanks,  Mike

[mu26aeh]

Are the decoders a tight fit in the frame ?  Might have to build up some solder on the contact pads where the decoder fits in the frame.  Also need to be certain the motor contacts are making a solid connection with the bottom of the decoder board.  Might need to adjust them to make better contact.

[gbcaboose]

I thought about that and on one of them I took the 4 "clips" off of the original light boards and crimped them to the 4 contact points on the decoder. This made for a really tight fit, but the results were the same. 

[peteski]

Most likely they need to be programmed on DCC to enable running on DC. CV 29 has a "alternate power conversion" (colloquially called "analog") bit in it which has to be set for the decoder to respond to DC.  DCC users often disable that feature and I think that the default factory setting is also to disable DC.

As far as the jerky running, it could be your throttle.  If it has a pulse setting, disable that and see if that improves running. Also, disconnect the throttle from track and then power the loco by taking a 9V battery and touching its terminals to the track (the terminal spacing is perfect for that - I often use a 9V battery to test my N scale trains).  A battery provides a pure DC to the track which is the preferred power for decoders running on DC. If it still runs poorly then there is another problem (dirty wheels.track or mechanical issues).

[gbcaboose]

Thanks Pete,

A ran the GP40-2's (actually a GP38-2 and a GP40-2) using a 9v battery and they ran much smoother. As for the GP30's, I'll wait until the next "run-night" with the club and see if the "programmer" can change the setting to run on DC as well as DCC.

Thanks again,  Mike

[Bendtracker1]

I think that the default factory setting is also to disable DC.

On all of the DIGITRAX chips I've installed peteski, the default is ON for DC.  As you stated, I always disable this function.
 

[gbcaboose]

The spec sheet for the DN163A4 says the default in ON for DC operation, but neither of the 3 I installed in the GP30's would operate. This afternoon I installed 3 Digitrax DN163A0 decoders in a pair of GP38's and a GP40. All 3 tested fine using a 9v battery. Since these 3, along with the GP40-2 and the GP38-2 I got from Dave Foxx all test good, but none of the GP30's will run, I'm thinking/hoping the spec sheet for the DN163A4 (GP30) decoder is wrong on the website and it defaults to OFF for DC operation.

As I stated in a previous post, the next "run night" I can attend with my club is in a month. I'll be able to program them then. The club president is supposed to be getting with the club's DCC "guru" to see if he knows what the issue might be and hopefully resolve it at the next meeting.

Mike

[peteski]

Mike, I'm pretty certain that those locos not working on DC just need the "DC" bit turned on in CV29.  You say that the lights flicker when you put the locos on the track powered with DC. That is a pretty good indication that the decoder is alive.  No DCC guru is needed.     Instead all you should need is a good CV 29 calculator. Here is a one which is clear and informative.

http://www.2mm.org.uk/articles/cv29%20calculator.htm

Or even simpler, make the contents of CV 29=6 (that is 28/128 speed steps, short address, and DC operation enabled).  That is usually the default setting.  Or make CV 29=38 (decimal). That is the same as above except with long address enabled. In DC you don't even care about the address. 

[mmyers]

I would check to see if motor contact is good. With the shell off, select the engine's address, turn the throttle up and press down on the board in the area of the motor. If if moves, fix motor contacts.
I have never known a Digitrax decoder to ship with DC conversion turned off. Actually, just about all decoders if not all come with analog conversion enabled. How else would someone without DCC turn it on?

Martin Myers

[jagged ben]

It may be the MRC Tech II, if it has pulse width modulation.  Digitrax decoders dont run properly on my Tech IIIs.  They kind of stop and start.  (NCE doesn't have this problem.)  I believe the decoder mistakes the pulse for a possible digital signal and drops out of analog mode.

Also I believe the lights need to have been left on during the last DCC use or they won't light up in analog.

EDIT:  I see some of this has already been said

[gbcaboose]

Just checking in to say that the problem has been solved. It appears that when I disassembled the GP30's, somehow the motor tabs got bent at about a 45 degree angle to the side and weren't contacting the decoder on the contact pad. Since the tabs aren't visible once everything was assembled I couldn't tell they were at an angle.  I knew the tabs were contacting the decoder by the resistance/springy-ness while pushing down on the decode while installing, I just couldn't tell the tabs were missing the pads. Now I have the tabs fed through the slots on the decoder contact pads and everything working great. Thanks for all the help and suggestions.

Mike

[jagged ben]

Yup, typical Atlas problem.  And the first reply to your original post mentioned it!  Glad it's fixed.

[tehachapifan]

Glad it is all working but the only thing that doesn't quite add up for me is that, if it was indeed the motor tables not making contact, you would still get lights. I tend to think that there is/was also a loose contact(s) with the frame that is not acting up right now.