Introduction
I purchased this beauty on eBay (from Australia!) circa September 2021 because it had scale profile wheels that allowed 2-rail DCC operation with a PS3 board. My past experiences converting O Scale 2-rail MTH locomotives are happy ones, and this conversion was no exception. This time, I decided to add a little wrinkle by retaining track-based 2-rail DCC operation, and I’ll show you how I accomplished this.
Conversion Process for Track or Radio-Controlled DCC Operation
The entire conversion centered around the tender – the locomotive was entirely untouched.
I mentioned in the Introduction that I wanted to retain the 2-rail track-powered operation, so after removing the tender shell (which is very easy: remove four screws, and you’re in!) I concentrated on the 2RAIL/3RAIL switch shown diagrammatically and pictorially below:
TOP VIEW OF SWITCH
3RAIL
Center loco roller (Br) ->| |<- (Bk) Rt tender wheels
PS3 (Tk R) (Re) <-| |<- (Gy) Lt tender wheels/tender frame/loco Lt wheels -> (Gy) PS3 (Tk L)
Rt tender wheels (Bk) ->| |<- NC
2RAIL
Depending on the switch position, the “two-position” switch electrically connects the center row of terminals to either the top (3RAIL) or bottom (2RAIL) row of terminals. The two columns of the switch are electrically isolated; i.e., each terminal in a row electrically isolates from the other.
From this “switchology,” it’s apparent that the “track left” comes from several locations on the center-right terminal, and one wire goes from this terminal to the PS 3 board. The “trick” is to move the several “track left” wires to the bottom-right switch terminal where “NC” was and leave the one grey wire leading from the center-right terminal to the PS3 board in place. Then, disconnect the wires on the top posts (originally for 3RAIL operation) and attach the DCC Track Right/Left outputs from the DCC amplifier that is, in turn, connected to the ProMiniAir receiver that collects RF DCC. Voila!
TOP VIEW OF SWITCH
RA (for radio control)
Radio Control Tk R ->| |<- Radio Control Tk L
PS3 (Tk R) (Re) <-| |-> (Gy) PS3 (Tk L)
Rt tender wheels (Bk) ->| |<- (Gy) Lt tender wheels/tender frame/loco Lt wheels
2RAIL
Dead-Rail Components Installation
Several Battery-Powered/Radio Controlled (BPRC or “Dead-Rail”) components required addition: an antenna, a power switch, a charging plug, a 14.8V battery, the ProMiniAir receiver, and a DCC amplifier. The picture above shows that the prominent speaker takes up a lot of real estate that we need for our Dead-Rail components. Sadly, the speaker had to go, replaced by a smaller speaker that I mounted in place with 2-sided tape.
The Tenergy 4S1P 14.8V battery has an extended, thin profile that makes a tight fit in the tender. The ProMiniAir receiver and the Cytron MD13S DCC amplifier fit nicely on the forward sides of the tender interior.
Antenna installation was easy, requiring drilling a small hole through the bottom of the tender. The ANT-916-CW-RCS is an excellent choice for a small 915 MHz antenna with a 3.3 dBi gain, and it is available from Digi-Key or Mouser.
I installed the charging plug in an empty hatch opening (with a bit of filing of the original opening) on the top of the tender and repurposed the “DCC/DCS” switch as the Dead-Rail “on/charging” switch.
Conclusion
Conversion of the O Scale MTH AC-6 Cab Forward was rewarding and straightforward. See the video below for the “proof in the pudding.”
