N scale Atlas GP15 decoder swap

[BOK]

I have tried un-sucessfully to swap a DC decoder for a Digitrax DCC one in a couple of GP15s. I have managed to swap the decoders physically and get the head lights to function either direction but they won't run. There also the little problem of the motor tabs to fit in the decoder slots.

Any other modelers have this challenge and how did you overcome it?

Thanks in advance.

Exprail

[nickelplate759]

If the lights work and respond to appropriate DCC commands, it's likely that those motor tabs are the cause of your problem.  I don't have a GP15, but on similar locos I have sometimes resorted to soldering the tabs to the board where the poke  through the slots.  Unfortunately that means they need to be unsoldered for maintenance, which is far from ideal.

[Lackawannae8]

I have tried un-sucessfully to swap a DC decoder for a Digitrax DCC one in a couple of GP15s. I have managed to swap the decoders physically and get the head lights to function either direction but they won't run. There also the little problem of the motor tabs to fit in the decoder slots.

Any other modelers have this challenge and how did you overcome it?

Thanks in advance.

Exprail

Ive been installing esu in these. the framework notches are a poor fit. I need to shim the esu board with copper tabs onto the wings of the decoder for some pick height. I also have been hardwiring the decoder to the motor.

[mu26aeh]

As nickelplate noted, if you have control of the headlights, the problem lies with the tabs not making good contact with the decoder pads.  Hardwiring or soldering the tabs to the board is the route needed to take.  Common issue with a lot of Atlas locomotives

[peteski]

With the shell off, turn the throttle and press down on the decoder in the area of motor contacts.  That will probably make the motor run.  Another possibility is that the motor contacts partially touches the slightly raised layer of solder mask coating outside of the metal contacts, causing the contact not to touch the metal pad.  You might have to bend the motor contacts slightly to make sure they are only contacting the metal pads on the decoder.  This contact design is basically sound, but sloppy manufacturing tolerances result in problems.

[BOK]

Thanks to all of you for your great information. I have some new decoders on the way to fix the problem.

Exprail

[peteski]

So what exactly did you determine was the cause of the problem with the original decoder (that just installing a new decoder will fix)?

[woodchip]

I’ve found it easier to leave the motor and drive train in one of the frame half’s, remove the other frame half and you’ll be able to feed the motor contact strips through the slots that most decoder boards have. Unless the board incorporates a socket to insert a decoder what’s advertised as plug and play isn’t.

[BOK]

Peteski you are right. I bought two more decoders this time TCS instead of Didgitrax hoping they would have tabs instead of slots ... but I was wrong. Same old same old connection.

Reading "woodchip's" post it appears the best way to swap the decoders is to take the metal, body halves apart making lining up the slots for the motor contacts easier.

The reason for getting my two GP15s DCC is that they are exact models of two prototype locomotives I used to start up the Wisconsin Northern  short line in 2004: WN 1500 (City of Bloomer) and WN 1501 ( City of Barron). These two locomotives were our only power and were good pullers originally from the Frisco...when running them as engineer you could still see scratches of SLSF orange.