USA Trains EMD GP30 Upgrade to RailPro

Garden Railroading
1

Locomotive: USA Trains EMD GP30
Stock PCB (brain): YD-249-PCB-01
Planned control: RailPro LM-5S-G with sound (hard-wire install)

What I’m doing

I’m replacing the factory electronics in a USA Trains GP30 with a RailPro LM-5S-G. Goal is simple, reliable motor control + lights (and possibly smoke later). I have the LM-5S-G manual and understand the basic RailPro wiring (track/battery power to PWR +/-, motor to M +/-, lights to function outputs).

What I’m seeing inside the GP30

Each motor truck feeds the stock PCB with three wires: black / red / white. On the PCB those 3-pin plugs are silkscreened U1 (one truck) and U2 (the other truck).

My questions

  1. What are “U1” and “U2” actually for on this USA Trains board?
  2. What does the third (white) wire from each truck do? Motor blocks usually only need two wires.
    IMG_0626.HEIC
    IMG_0626.HEIC3024×4032 2.82 MB
1 Like
2

Not much experience with USA locos. Hopefully you can get a schematic of the GP-30. Otherwise, you may have to open up the motor blocks and see how it’s wired. I suspect the 3 wire is 2 wires taking track power to the PCB, and a third wire to the motor through a switch that would allow parking the engine with the lights on. Just a guess, however…
Paul

3

U1 and U2 are not related to the motors, they are constant voltage providers for either the lights or the smoke units, and each works in a different direction (that is why there are two). If there are three wires coming out of the power trucks then the engine is really old, and one of the wires is common + or -. and you will only need two wires to run the motor - testing will determine which two .