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Upgrade MTH F3 ABA with FT ABA

Tips for Success and Detail Information


  • When doing Conversions digital photos are invaluable.
  • If you don't use a grounding wrist strap, handle circuit boards with clothes dryer sheets to avoid static electricity.
  • Deburr all holes and keep metal particles away from all electronics.
  • While relocating parts, consider how the harnesses will be routed.
  • These parts were moved from 20-2272-1 Rio Grande FT ABA

These parts were moved from MTH #20-2272-1 Rio Grande FT ABA

Four motors, PS2 circuit boards (master and slave), Lighting circuit board and lamps, Volume control, Speaker, Coil couplers, and Wiring harnesses

Color Codes for Circuit boards and Wiring harnesses in FT As

Lights: MarsLight - White Plug (top headlight)
I/L - Interior - Yellow Plug
D/L, N/L - Number Boards - Red Plug
H/L,B/L - Headlight - Green Plug (bottom headlight)
Also CPLR - Coupler - Blk Plug


Trailing FT A Lighting/Coupler Harness (this harness will go from trailing F3 A to slave on F3 B unit)
Grn & Red - Contacts for Rear/Red lights in shell (cut these unneeded wires)
Brn & Prp - Mars Light - Wht Plug
Blk & Prp - Number Boards - Red Plug
Or & Prp - Coupler - Blk Plug
Blu &Prp - Headlight - Grn Plug
#2 Blu &Prp - Int Light - Yel Plug_12.JPG


My Attempt to mount the socket circuit board on the truck housing back of the leading F3 unit failed.  The FT sockets were mounted under the rear coupler of the A and B units.

I tried drilling the F3 A unit for 2-56 machine screws and had no success. I have it from two knowledgeable sources that holes for 4-40 screws can be drilled and tapped. Hopefully existing holes can be enlarged. Use cutting oil for aluminum while drilling and tapping. As you drill into the trucks you get in so far and then feel like you hit granite. Mark your depth needed and proceed very carefully. That's where my drill or tap breakage occurred.

The F3 motors will not fit into the FT units. The FT keyways are too small.

Parts Info from PS2 FT ABA MTH #20-2272-1 built 2002:
  4 MOTORS - RS-385PH or RD 521115 Made in China
  Coil Coupler resistance PS2 FT 5V = 3 ohms PS1 F3 = 5.5 ohms

Both Speakers are a scant 2" diameter. Markings were:
F3 speaker - STAR PR-05004-08 8 ohms 0.2W KOREA 612V
FT speaker - STAR PR-050-A1111 16 ohms MAX 2W 1215


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