Athearn SD70I - Going DCC but I have the DCC-hostile version!

[ryan_wilkerson]

So my son purchased an Athearn SD70I and since I already have a Santa Fe version, I thought I could drop in a TCS K1D4 like I did in that one. Opening it up, it looked different so I did some research and found this on the Spookshow website, along with a photo of the exact unit I'm working on, CN 5701:

"Sadly, this version wound up being out-and-out DCC-Hostile"
http://www.spookshow.net/loco/athearnsd7x.html

The "DCC-hostile" comment made me think of using a Kato mechanism, if one would work. I have a spare SD70MAC mechanism but it looks a bit longer. SD70M mechanisms are harder to come by so maybe I should just stick with figuring out how to get DCC installed into the Athearn mechanism. If someone has used a different mechanism, I'd like to hear about it.

So can anyone with experience putting DCC into this version offer some advice? I have a spare TCS "CN" decoder and can hardwire if that is recommended.
Thanks for the help!

[jdcolombo]

Hi Ryan.

I don't have one of these, but from reading the description on Mark's site it sounds like the problem was with the design of the motor-to-lightboard contacts (since they ended up with the 5-pole Mashima but different contact strips to cure the problem in the final design).   So what I would do is hard-wire a decoder, and make sure that you wrap where the wires get soldered to the motor brushes with kapton or electrical tape to prevent them from contacting the frame.  From the photos the site, it looks to me like the easiest hard-wire solution would be to cut the lightboard into two pieces, keeping the front piece for the front headlight and for the decoder power pickup (you'd solder the red/black wires to the power traces on the front piece of the board).  You might also be able to cut it in THREE pieces and salvage the rear piece, too, for the rear light and redundant power pickup, and place the decoder in the middle between the two or underneath the rear light board piece where the notch in the frame is. There looks to be plenty of space in either spot for an ESU LokPilot Micro or Zimo MX621, which would be my first choices for hard-wiring (but I suspect any tiny decoder, like the Digitrax DZ series or TCS Z2 would work).  A TCS CN might work, but you'd almost certainly have to lengthen the wires between the pieces, and I don't know if they would fit on this frame in the pickup notches.  You could certainly test fit it, though - if the pieces fit in the pickup notches, there is no reason why the TCS CN shouldn't work in this application with some wire lengthening.  But I'd probably do this by cutting the lightboard.

This really shouldn't be all that hard.  If you've installed hard-wired decoders before, I'd say you could do this in an hour.

John C.

[Big Train]

Just to add to jdcolombo's idea. If you go here:

http://n-scale-dcc.blogspot.ca/search/label/Loco%3A%20Athearn%20F59PHI

there are instructions for installation of the above mentioned decoders (or similar)  in the F59PHI using either the original Athearn board or modifying an Atlas GP 40 board (?). I don't know how similar the F59 board is to the one in your SD70I. I suspect it may be similar in design and pattern.

Good reference website, nonetheless, and there are ingenious work-arounds. Perhaps if you check the other installs on this site, you may find an alternative method or idea to solve your particular situation.

Adapt. Modify. Overcome.

Hope this helps....

[ryan_wilkerson]

John, thank you for your thoughts on this conversion. I'll open it up tomorrow and see how the decoders I have measure up. I think I have a spare Z2 also. I'll update here as I get into it.
-Ryan

Hi Ryan.

I don't have one of these, but from reading the description on Mark's site it sounds like the problem was with the design of the motor-to-lightboard contacts (since they ended up with the 5-pole Mashima but different contact strips to cure the problem in the final design).   So what I would do is hard-wire a decoder, and make sure that you wrap where the wires get soldered to the motor brushes with kapton or electrical tape to prevent them from contacting the frame.  From the photos the site, it looks to me like the easiest hard-wire solution would be to cut the lightboard into two pieces, keeping the front piece for the front headlight and for the decoder power pickup (you'd solder the red/black wires to the power traces on the front piece of the board).  You might also be able to cut it in THREE pieces and salvage the rear piece, too, for the rear light and redundant power pickup, and place the decoder in the middle between the two or underneath the rear light board piece where the notch in the frame is. There looks to be plenty of space in either spot for an ESU LokPilot Micro or Zimo MX621, which would be my first choices for hard-wiring (but I suspect any tiny decoder, like the Digitrax DZ series or TCS Z2 would work).  A TCS CN might work, but you'd almost certainly have to lengthen the wires between the pieces, and I don't know if they would fit on this frame in the pickup notches.  You could certainly test fit it, though - if the pieces fit in the pickup notches, there is no reason why the TCS CN shouldn't work in this application with some wire lengthening.  But I'd probably do this by cutting the lightboard.

This really shouldn't be all that hard.  If you've installed hard-wired decoders before, I'd say you could do this in an hour.

John C.

[ryan_wilkerson]

Thanks for the link Big Train. I'll take a look and see if there are similarities with the F59 install.
-Ryan

Just to add to jdcolombo's idea. If you go here:

http://n-scale-dcc.blogspot.ca/search/label/Loco%3A%20Athearn%20F59PHI

there are instructions for installation of the above mentioned decoders (or similar)  in the F59PHI using either the original Athearn board or modifying an Atlas GP 40 board (?). I don't know how similar the F59 board is to the one in your SD70I. I suspect it may be similar in design and pattern.

Good reference website, nonetheless, and there are ingenious work-arounds. Perhaps if you check the other installs on this site, you may find an alternative method or idea to solve your particular situation.

Adapt. Modify. Overcome.

Hope this helps....

[rrjim1]

I installed TCS Z2 decoders in two of these locos. I did a very small amount of milling for the wires, and used TCS SM LEDs for the lights, instead of the light board.  The Z2 is a small DCC decoder with very good motor control, the Digitrax DZ 126 would also be another great choice.

[peteski]

Digitrax DZ126T is even closer in size to TCS Z2 than DZ126.

[ryan_wilkerson]

So it took me some time to get into this project. I looked into a TCS CN decoder but it didn't fit nicely so I looked at others that I had. I came across a TCS M4 and it fit perfectly under the stock lightboard. I did remove the two LEDs on the lightboard and since the solder pads in the middle of the board were available, I used those as the power pickup for the decoder (red and black wires). I then routed those underneath the board to the M4 at the rear of the SD70I. The grey and orange wires (motor) were routed to the top and bottom where the small motor leads are located. I soldered them and then made a Kapton tape sandwich to make sure nothing would touch the metal chassis. I had to do a little filing on the frame and plastic motor cradle to get the orange and grey wires to fit snugly but not be pinched. At this point, I wanted to make sure it worked. I took it to my programming track and after a couple minutes in JMRI, it was programmed to the road number 5701. Tested back and forth and it runs great! Now I need to work on adding the headlight and tail light with some prewired TCS sunny white LEDs. It would be nice to also get the ditchlights to work but we'll see about that in the future. I can't wait to surprise my son with this project when he gets home tomorrow! Here are a few photos. I know it's not the cleanest install but it's only my second or third.

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[ryan_wilkerson]

I want to thank everyone who replied with help and advice. I wouldn't have tried this without your input...the locomotive would have just been sitting in the box and not on the DCC mainline where it sits tonight!

[peteski]

Nice install Ryan - looking good (and it works too)! 

[ryan_wilkerson]

Thanks Peteski...working in the most important part but I'm glad it looks decent too.