Adding a DCC Sound Decoder to N Scale F59PHI

A couple of months ago I stumbled on an Athearn F59PHI, Sounder #902 (ATH10015) in my local hobby shop here in Seattle. This model was made back in 2002 so no drop-in decoders exist.

Since this is a a local favorite of mine I figured I’d give it the full-out sound decoder treatment. I did some rough measurements and I figured I could make the  Digitrax Standard 1 Amp Sound Decoder (SDN136PS) work. If sound isn’t important to you, it seems like there are far easier decoders you can get to fit inside like this guide using a DZ series decoder.

Testing the Fit

Athearn F59PHI with the shell and stock light board removed.

The first thing I did to prep the model was removing the stock light board and measuring out two pieces of styrene to protect the gears from loose wires.

I placed the decoder roughly where I expected it’s final location to be (speaker to the rear since the area above the shaft is longer.) Conveniently the clips for the stock light board happed to fit at each end of the decoder with the wires pinching to hold everything in place.

Using masking tape to hold everything temporarily in place as I went, I test to see if the shell could still close bundled up this way. Success.



First I removed the 8-pin harness from the decoder and used the soldering iron to remove the cables from the included plug. The instructions suggest cutting the cable but because I didn’t know how far any of them would have to reach I figured it was safer to preserve as much as possible.

Next I prepped my forward LED to be installed. As a bit of caution, I used a square LED because it fit perfectly in the space, taking no more room than it needed to. I neglected to consider how much wider the viewing angle was with this type. If I were to start over I would cover the tip of the LED with masking tape and paint the rest of the LED body black.

Clipping the LED as short as I felt comfortable, I attached a 270Ω resistor to the cathode. Consider using a higher value resistor. I used a 270Ω because of the suggestion in another guide but for the white LED it’s probably too low.

I wrapped each lead with Kapton tape and then wrapped the whole assembly with it to protect from shorts.


Next I removed the motor assembly to attach the pickup (red, black) and motor wires (orange, grey). The black plastic shell slides off allowing easy access to the points.

Carefully run the wires through the top of the black cover to conserve the most space and solder the appropriate motor power wires. These are hallow metal pins with a spring inside. While soldering the wire down, the heat caused the spring to expand on one side and pop out. It was a pretty simple fix but confused me when it happened.

Once you’ve soldered the motor lead, take a piece of Kapton tape and cover the attachment so the pickup leads can’t touch.

Following the same step, do the same with the pickup lead. Pay attention to the black cover’s openings so you can best place the wires to not bulge.

After you’ve done this with both sides, slide the black cover back in place making sure not to damage any of the connections. I gently pulled the sides away from the model until the clips were close to the bottom.



I glued the LED and resistor into place using white glue so it could be removed if needed. Set the shell and chassis aside close together as to not strain the wires until the glue has completely dried.

Because I neglected to stop the LED from spreading light in all directions, light leaked into the cab and out through the front bogie. While the lit cab actually looks pretty good, the light leaking through the bottom needed to be corrected.

I reopened the model and covered the whole forward LED and light pipe area with electric tape. This reduced the brightness of the leak but didn’t completely stop it.

Reverse Marker Lights

When assembled I notice that the red marker lights glowed while the lights were on. Clearly not a desired effect. While I didn’t plan on adding a separate light for the markers, the leak made it easier to just add one in while I was at it.

As with earlier, I used a red LED and resistor, soldered it to the decoder and then glued two .75mm fiber optic strands. I used a paint marker along the strands to stop light from leaking both out and in to the strand.

After the glue had dried, I covered the light with electrical tape to about an inch down the strand from the seam.

I then taped the led into the indent on the top side of the decoder, carefully thread the strands through the holes and placed the shell back over the chassis.

Finally a drop of super glue at the base of the light strands to hold them in place. When dried, I cut them back to the front of the model and filed the tips down.

Final Assembly


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