Upgrade MTH SP AC-6 Cab Forward Page 2 of 2
This 20-3025-1 Southern Pacific AC-6 Cab Forward was listed in the MTH 1998 Volume 1 Catalog.
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. Page 28 of the MTH Cab Forward Operating Manual shows the location of the 4 body mounting screws for boiler removal.
Boiler
(No drilling or grinding is required - just a bit of razor
sawing/filing on smoke unit board.) The fun part is adding nine more
harness wires and keeping that nice open space between the boiler
and chassis.
Secure wires to boiler and motor with premium grade 3M electrical
tape. (about $8 a roll)
Use the 3V battery to test lights, smoke fan, smoke
heater, etc. before installation.
During the installation keep the shell near for visual check
fitting.
Note part locations for reinstallation.
P. 26 The spacer for the harness socket is not needed.
The additional red wires are not needed if the existing roller pickup wires test okay.
P. 29 Connecting The PS-2 Harness To The Smoke Unit
After smoke unit modification, test the fan direction with the
charged tender battery.
Front of Boiler Before Upgrade
After the PS2 harness is installed, the fun part is routing all the wires. The tach reader wires can be routed similar to the existing motor wires.
P. 23 Determine Engine Motor Type
There is a Pittman motor that requires a 1/16" Allen Key for
flywheel removal.
P. 24 Installing Tach Tape Onto Motor Flywheel - Center tape on
flywheel.
P. 25 Mounting Tach Reader To Tach Reader Bracket - Remove tach
reader spacer as shown.
Test original motor wires routed along
chassis for good insulation and continuity. If okay, keep the
original motor wires connected and routed to the harness board area
in the back.
The Tach Reader harness wires must be lengthened.
P. 27 Connecting Headlight
Bulb & Wire Harness
The cab must be removed to install the PS2 Headlight bulb. Remove 4
screws for cab removal. The two center screws hold the backhead in
place.
The cab must be removed to install
the PS2 Headlight bulb. Remove 4 screws for cab removal. The
two center screws hold the backhead in place. |
Secure Wires in Boiler above Motor.
Sleeve the wires secured by metal hold down strap. The metal
strap will cut insulation. |
| P. 31 Connect
Power To The Constant Voltage Board The inductor can go into the boiler shell. The board does not need to be removed from the boiler. |
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Remove smoke switch from front spring contacts and use the cut red wires as jumpers to join the spring contacts together. Tuck the soldered insulated splices under the motor.
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P. 27 Connecting Motor, Ground & Pickup
Wires - (in back near circuit board)
The original motor wires can be attached to the harness near the
rear of the locomotive. Original motor wires are Brown and Black. Connect
the white harness wire to the brown motor wire and connect the
yellow harness wire to the black motor wire.
Tie the harness ground lead to a rear gear box screw. The harness
red pickup roller wire can be spliced to the existing pickup roller
wires.
Both gear box covers must be tight.
Now what? Six wires must be routed to the enclosed boiler area while keeping a low profile.
Test system before proceeding with wire management.
The kit plastic wire wrap sleeving is
too large for the smoke and headlight harness wires over the gear
box. If small black thin flexible wire sleeving is unavailable, use
premium electrical tape for low profile.
Fabricate 3 wire hold down straps using metal tabs similar to the
ground lead tab. Strap tabs must be metal so gear box screws can be
as tight as possible.
Secure sleeved/wrapped wire to hold
downs with 22 gauge solid black wire used as tie wire.
The metal plate behind the back gear box is bent up slightly on both
ends to take pressure off wires entering and exiting below the metal
plate.
Double check wire placement before attaching boiler.
Lost Clear Space under Boiler
P. 34 Loading The PS-2 Sound File Into The Upgraded Engine
Use Premier AC-6 Cab Forward 20-3349-1 (2008 Vol. 1) sound
file.
MTH Loader Files work better if you put them in their Default
folders in Windows Program Files.
Be sure you have the latest version of the MTH DCS Consumer Loader.
Before downloading the sound file, specify saving it to the Desktop.
In Windows Vista, see file in Windows Explorer after downloading and
look under Compatibility Files (Window top bar). When you find the
file after downloading, go to Properties and click Unblock under
Security at the bottom of the page. You can then move the file to
your MTH Files in the MTH DCS Consumer Loader folder.
If your TIU has the RS-232 computer input socket use a RS 232 to USB
Converter (mine is from MCT Corp.). The sound file download will
take about 40 minutes with that connection.
Be sure remote batteries are good so you can shut off smoke as soon
as download is complete.
After sound file is installed, name engine, shut down, and remove
power.
| Here is the finished Cab Forward with smoke coming out of the back of the engine. |
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