Dead-Rail Conversion of an MTH PREMIER NORFOLK SOUTHERN SD60E DIESEL (O Scale, 2-Rail, PS-3.0): A Follow-up

To change things up, I showed you a “simple” Dead-Rail conversion of a Diesel locomotive in my previous post. This post follows up with an even more straightforward conversion that is very similar to what I do with steam locomotives: leave the DCC decoder and electronics in the locomotive alone except to provide a plug connecting the locomotive’s DCC decoder to an external Dead-Rail DCC source instead of DCC from the rails, which in our case will come from a battery-powered radio receiver and amplifier mounted in a “battery car” (the tender for steam locomotives).

Let’s see how this is done. I will repeat some steps so you do NOT need to refer to the previous post.

The Locomotive Conversion

The first step is to remove the locomotive shell so that we can modify the “2-Rail/3-Rail switch” and convert it to a “2-Rail/Dead-Rail” switch that will maintain the ability to use track power in either DCC or DCS mode and add the ability to use DCC from an external source.

Removing the upper plastic shell was easy; remove eight screws and the rear coupler. That’s one of the beauties of MTH locomotives: they are well-designed for disassembly.

There are four screws to remove at the front and rear of the “speaker pocket” in the middle of the locomotive.
The rear coupler must be removed to access the screws at the locomotive’s rear.
There are four screws to remove at the front and rear of the locomotive. The Kadee couple must be removed to access these screws at the locomotive’s rear.

Separating the chassis from the upper shell, we see the “stand holding the switch we’ll modify.

Side view of the locomotive Interior

Repeating from my previous post: To allow track-based “2-Rail” or “Dead-Rail” Operation, we need to figure out how to get DCC from either the track (“2-Rail Operation”) or from the output of the ProMiniAir Receiver’s Amplifier (“Dead-Rail Operation”). The original 2-Rail/3-Rail switch that routes track power/signal to the PS-3.0 is shown below.

The original 2-Rail/3-Rail switch routes track power/data to the PS-3.0.

These connections were verified by using a multimeter’s resistance-measuring capability. Let’s see how this switch is designed:

When the switch is in the 2-Rail position:

  • The Right Wheels’ output is directed to the PS-3.0’s DCC Track Right by shorting the “Track Right” end post to the “Track Right” center post.
  • The Left Wheels’ output is directed to the PS-3.0’s DCC Track Left since it’s directly soldered to the “Track Left” center post.

When the switch is in the 3-Rail position:

  • The Center Rollers’ output is directed to the PS-3.0’s DCC Track Right by shorting the “Track Left” end post to the “Track Left” center post.
  • Both the Left and Right Wheels’ output is directed to the PS-3.0’s DCC Track Left by shorting the “Track Left” end post to the “Track Left” center post and the “Track Left” end post’s jumper to the “Track Right” end post on the opposite side of the switch. This connection shorts the Right Wheel’s output to the Left Wheel’s output on the center post that then goes to the PS-3.0’s Track Left!

The photo below shows how to rewire this 2-Rail/Dead-Rail Operation switch.

The original 2-Rail/3-Rail switch has been rewired for 2-Rail/Dead-Rail operation.

Repurposing this switch has the following features:

  • The output from the center rollers is disconnected and closed off. Its role was only for 3-Rail Operation.
  • The Right and Left Wheels’ outputs are located on separate posts at one end of the switch (for 2-Rail Operation in either DCC or DCS mode).
  • The Track Right/Track Left DCC outputs from the ProMiniAir Amplifier are located on separate posts at the other end of the switch (for DCC Dead-Rail Operation).
Before/After switch schematics

After remounting the newly-modified 2-Rail/Dead-Rail switch back into its stand, the Dead-Rail wires leading to the switch are connected to wires that have an external plug that will receive Dead-Rail DCC from the “battery car” we’ll describe below.

The Dead-Rail connector from the 2-Rail/Dead-Rail switch to the small external Dead-Rail DCC connector.

A plug is “snaked out” near the rear coupler to connect to the external source of Dead-Rail DCC from the “battery car.”

The Dead-Rail connections between the “battery car” and the locomotive. That’s it: two wires.

Once we screw the upper shell back in place, we are done with locomotive modifications!

All we did was modify one switch and route the new switch connections to a small plug snaked out near the coupler. It can’t be any simpler than that!

Let’s turn to the straightforward “battery car.”

Battery Car Conversion

The photo below shows the components we fit inside a “battery car:” a 14.7V battery that will just fit through the door and a ProMiniAir Receiver/Amplifier. A surface-mount Molex 21004 antenna was mounted to the external metal shell. Surprisingly, reception worked, despite the traditional practice of avoiding antenna mounts on metal surfaces.

A straightforward “battery car” contains the battery and the ProMiniAir Receiver/Amplifier, and a surface mount antenna. Surprisingly, the surface mount Molex 211140 antenna worked OK when mounted externally to the car’s metal shell.

A small hole was drilled in the bottom of the car to pass Dead-Rail DCC from the ProMiniAir Amplifier to a plug that connects to the locomotive.

The small connector exiting the “battery car” that carries Dead-Rail DCC from the ProMiniAir Recevier to the locomotive.

Demonstration

With these Dead-Rail modifications, the video below shows Dead-Rail Operation.

The demonstration of Dead-Rail control using a Standalone ProMiniAir Transmitter controlled by a WiThrottle app on a smartphone. The DCC is wirelessly transmitted to the “battery car’s” ProMiniAir Receiver, providing high-power DCC to the locomotive.

Final Thoughts

The Dead-Rail modifications described here maintain 2-Rail Operation in either DCC or DCS mode, which mode is selected by the DCS/DCC switch.

The 2-Rail/3-Rail switch is repurposed as 2-Rail/Dead-Rail. The DCS/DCC switch is unmodified.

If the 2-Rail/Dead-Rail switch is set to “Dead-Rail,” then the DCS/DCC switch MUST be set to “DCC” so that the PS-3.0 can interpret the DCC signal coming from the ProMiniAir Receiver/Amp in the “battery car.”

This conversion was straightforward:

  • Modify one switch in the locomotive to receive DCC from an external source.
  • Snake a connector from this switch out of the locomotive near the coupler
  • Insert a battery and ProMiniAir Receiver/Amp inside the “battery car.”
  • Snake a connector from the Amplifier out of the “battery car”
  • Connect the two plugs together and couple the car to the locomotive.

I hope this simple conversion will inspire you to try your own conversion! There are locomotives such as PS-3.0-equipped MTH that will make this process easier.

Dead-Rail Conversion of an MTH 2-Rail O Scale 4-6-2 K-4S

Presents the dead-rail (battery power, radio control) of an MTH O scale, 2-Rail K-4s steam locomotive with PS-3.0.

Introduction

I obtained this 2-rail O scale MTH 4-6-2 K-4S (MTH 20-3473-2) on eBay circa November 2020. This model is unusual because it’s a 2-rail version with “scale wheels” and is equipped with a PS-3.0 control board that can operate in either DCS or DCC mode.

Box information on this locomotive

The Good News: No extensive 3-rail to 2-rail conversion was necessary, and no new DCC decoder was required.

The Bad News: This locomotive contained a PS-3.0 board in the tender I had not seen before. Also, this was my first conversion of a 2-rail MTH locomotive, and I had a few issues to learn!

Close-up of MTH PS-3.0 board for the MTH K-4s

Well, let’s seen how to proceed to convert this loco to DCC dead-rail operation.

Analysis of the Electrical Connections

I’ve done several MTH 3-rail conversions with PS-3.0 boards. Still, this locomotive was designed quite differently: it has a switch to select 2-rail or 3-rail operation (a potential problem) and another switch for DCS/DCC operation (easy to take care of).

Bottom view of tender showing switches and electrical pickups. Before dead-rail modification, the grey wire connected the rear left wheels’ voltage to the tender frame, and the brass spring connected the front right wheels’ voltage to the black wires inside the tender.

This is a bit complicated. With this original design, the tender frame assumes the voltage from the tender’s uninsulated rear left wheels (whose right wheels are insulated) via a grey wire connected to the tender frame, which under 2-rail operation is “DCC track left” inputs on the PS-3.0 board. The right track’s voltage is picked up through the copper pickups connected to the tender’s uninsulated front right wheels (whose left side is insulated) and is connected by black wires inside the tender. In 2Rail operation, the 2Rail/3Rail switch will connect these black wires’ voltage to the “DCC track right” on the PS-3.0 board.

Under 3Rail operation, the left/right rails are connected electrically as ground or “DCC track left” (and the frame is now either ground or DCC left rail voltage). A grey wire from the locomotive (which is electrically connected to the locomotive’s center roller pickups) is connected as “hot” or “DCC track right.”

In the original design, several grey wires are connected to the tender frame to pick up the “DCC track left.” Our job is to completely isolate both DCC track right and track left so that the DCC amplifier we add will be the only source of DCC, completely isolated from the tender frame, which will become our battery ground.

We always want to operate in DCC mode, so we need to disable DCS operation permanently.

The following images demonstrate my modifications to isolate all DCC from the frame and permanently enable DCC operation.

These images show several important conversion steps:

  1. Cut and seal off the two wires connected to the DCS/DCC switch. This will permanently enable DCC operation.
  2. Cut and seal off the grey and red wires to the center posts on the 2Rail/3Rail switch to ensure the DCC track’s total isolation right and left from any other electrical connections. This step will ensure no unexpected connections because of this switch’s setting.
  3. Disconnect the two grey wires mounted to the tender frame by one of the mounting screws holding the PS-3.0. One of the grey wires goes to the underside connector on the PS-3.0 board, and it needs to be connected to the DCC Amplifier’s “DCC Track Left” output. The other grey wire electrically connected to the tender’s left wheels should be sealed off. This step electrically isolates the tender frame from any other electrical connections, allowing it to act safely as a ground.
  4. Provide DCC “Track Right/Left” connections from the DCC amplifier (which we will add) to the two grey (DCC Track Left) and two red (DCC Track Right) inputs on the PS-3.0 board. We mentioned one of these connections in step 3, and the other pair of DCC “Track Right/Left” inputs go to the “Track” connector on the side of the PS-3.0 board.
Wiring modifications to isolate DCC from the tender frame and permanently enable DCC operation
Isolation of DCC track left from the tender frame

We need to move the PS-3.0 board forward slightly to make room for the battery, antenna mounting, battery switch, and charging plug. Also, we need to bend down the right side of the PS-3.0 board to provide sufficient clearance for the RF receiver/DCC amplifier that will be mounted on the inside top of the tender shell above the PS-3.0 board.

Also, I removed the two super-capacitors on the PS-3.0 board. The locomotive will then immediately turn off when battery power is turned off: we have no worries that power will be temporarily interrupted as with track power. I like the locomotive to turn off when I disconnect the power. This is not a required modification!

Moving the PS-3.0 board forward to accommodate the battery
Cuts of 2Rail/3Rail switch wires and charging plug mount
The 2Rail/3Rail switch center posts are disconnected
New DCC connections from DCC amplifier to two plugs on the PS-3.0 board
DCC connection to the underside of the PS-3.0 board. This image’s purpose is only to show one of the two plugs where DCC inputs to the PS-3.0 board.

Dead-Rail Additions

The tender modifications to add a 14.8V LiPo battery, antenna mount, battery switch, and charging plug can be seen in several images above. There is nothing unusual about these additions.

I used a Tam Valley Depot DRS1, Mk IV receiver with a U.FL external antenna plug rather than my ProMiniAir receiver and separate DCC amplifier because of space considerations. The Tam Valley’s DCC “Track Right/Left” outputs are connected directly to the two “track right/left” inputs on the PS-3.0 board (on the side and bottom connectors of the PS-3.0 board), as shown in the images above.

Conclusions and Warnings

I cannot emphasize enough the need for complete isolation of the tender frame ground from the DCC voltages output by the DCC amplifier that provides inputs to the PS-3.0 board. If you inadvertently leave a connection of tender frame ground to DCC left (from various grey wires), you may cause a severe short circuit, or the PS-3.0 board will not operate properly. Trust me, I know from a couple of bitter experiences…

Still, this was a fun and reasonably-easy dead-rail conversion, especially so since I didn’t need to modify the locomotive at all.

Here’s the final video of the fully assembled dead-rail locomotive. The PS-3.0 provides a number of DCC functions including:

  1. Directional lighting on/off (F0)
  2. Bell (F1)
  3. Horn (F2)
  4. Start-up/Shutdown (F3)
  5. Passenger/Freight Announcements (F4)
  6. Marker/cabin/firebox lights on/off (F5)
  7. Speaker volume (F6)
  8. Smoke unit on/off (F12)
  9. Smoke unit volume control (F13)
  10. Numerous other features (F0 through F28 are all active). See the Users Manual for extensive details.
Locomotive with final dead-rail installation

Thanks for dropping by!