Upgrade MTH SP AC-6 Cab Forward Page 1 of 2
This 20-3025-1 Southern Pacific AC-6 Cab Forward was listed in the MTH 1998 Volume 1 Catalog. When it died it was an excellent candidate for a PS2 Upgrade. It's a little confusing to run.
The upgrade was done in April 2012 using a MTH PS2 Upgrade Kit with the included Steam Locomotive Upgrade Kit Installation Manual - 4th Edition. The page numbers refer to the pages in that manual. When following the Installation Manual the color illustrations in the website manual are helpful.
Step by Step Conversion Process
Tips - For a better grip, a big handled
screwdriver is essential for loosening and tightening screws.
Wire management is critical. Keep in mind from start to finish. This
PS1 Cab Forward was toast because factory had cut power wire
insulation with a metal hold down strap.
Be sure all retained components and wiring is sound.
Tender - Mount Circuit Board
Charge the 3V battery and use it to test lights, smoke fan, smoke
heater, etc. before installation.
Plan the installation and do all drilling and grinding before
installing the PS2 board. Remove the old battery stickum.
P. 10-13 Mounting the PS2 Board - The tender is too narrow for angle mounting or side mounting. The metal heat sink bracket must be mounted on the end of the circuit board.
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| To fit heat sink bracket to the bridge rectifier, enlarge the rectifier hole with a Dremel cutting tool (a drill bit grabs and shatters rectifier). While grinding, protect PS2 board with a mask. Hold rectifier top gently with vise grips. | For mounting the heat sink bracket use a flat head machine screw for clearance. The photo shows a 8/32 FHMS because I stripped the 6/32 threads in the heat sink bracket. |
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Chassis Mounting Holes
P. 20 Installing the Battery and Volume Pot - Charger Socket - Cut the rectangular hole for the charger by drilling two holes and shaping with grinding wheel and file. This is easier with sharp files and new grinding wheels.
Move the original smoke on/off switch from the Boiler to the Tender for the switch plate.
| P. 20 Installing the Battery and Volume Pot - Charger Socket - Test charger plug in the installed socket for fit. The socket is easily squished if hole is too small. |
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P. 19 Wire and install speaker before the PS2 Board is installed.
Tender - Install Wiring Harness
After the PS2 Board and speaker are installed, the tender harness must be threaded through the shell entry hole from the outside (never to be parted from the shell again).
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Wire the volume pot before reinstalling in the original position. The chassis front bracket opening for the wire harness strain relief must be enlarged for the PS2 larger harness. (Use MotoTool) The bracket enhances wire management.
P. 14 The plastic insulator EE (for coupler) isn't needed for this installation. P. 17 The 8 PIN socket is unused.
The kit battery is installed in the original battery location.
