AML GP60 electronics

Overview

This is a technical page, but it needs to go into details due to the weird electronics in the loco, and lack of documentation.

I'm going into these details to document the interface presented on the motherboard, specifically to adding a different decoder.

So in not-so-infinite-wisdom, AML decided to use a non-standard socket in the GP60, even though there are thousands of Aristo/Bachman socketed locos and several decoders that fit THAT STANDARD socket:

  • Phoenix SM-18 decoder
  • TCS Wowsound 501 decoder
  • Digitrax DG583s QSI Revolution decoder (out of production)
  • QSI Titan decoder (out of production)

So this page is starting the arduous process of documenting the socket, the operation of the "dummy plug" and the eventual installation of an adaptor to facilitate the installation of ANY decoder.

 

LokSound decoder connections

 

Below is the pinout of the LokSound 5 XL decoder... pay attention to the fact that pin 1 has a square outline.

I'm calling the leftmost connector J1, as it maps similarly to the industry standard Aristo and Bachmann sockets. This is where track and motor and headlights are

I'll call the rightmost connetor J2, the top (in this illustration) J3, and the bottom J4

(THIS ILLUSTRATION IS FROM THE "BOTTOM SIDE" of the decoder)

LokSound 5 XL pinout

GP60 Motherboard decoder socket connections

 

 Below is a picture of the motherboard, notice it's orientation is such that pin #1 is nearest the bottom on the left and right connectors. Also pin#1 on the lower horizontal connector is on the left. The top connector is not labelled the same way, but we don't care since it is mostly servos.

20240205 183919

Again using my nomenclature:

  • Left Side: J1, #1 pin at bottom
  • Right side: J2, #1 at bottom, but NOTE: the first pin of the decoder does NOT have a socket hole... so the J2 socket starts with the rear light, not AUX 11, weird. You can see on the motherboard there is actually a hole in the board, but it's not used
  • Bottom, J3, pin one on the left
  • Top, J4, pin 1 on the right, but the numbering is screwed up when looking at the decoder illustration. No matter, mostly servos.

Listing of the pins in the socket J1: (notice I reference the actual pins in the socket)

 

J1 socket pin numberUSE                 notes                              
 1 left rail pickup 
 2 right rail pickup 
 3 right rail pickup (optional) duplicate of to pin 3
 4 right motor motor plus
 5 U+ (common pole) no idea
 6 U+ common pole tied to +UB on motherboard
 7 GND 
 8 left motor motor minus
9 wheel sensor inputreference to ground or plus?
10 left motorduplicate motor minus
11 speaker 1 #1speaker minus
12 speaker 1 #2speaker +

 

So most of what we want is here, the U+ things are not identical on the motherboard, so several things to check out.

J2 socket pins: (again I am referencing the pins in the socket, which are NOT numbered the same as the decoder, the decoder has 14 pins, the motherboard socket only has 12)

J2 socket pin numberUSE                 Notes                                                                                                 
 1 rear light 
 2 headlight 
 3 sensor input #1 
 4 AUX1 
 5 AUX2 
 6 AUX3 
 7 sensor input #2 
 8 AUX4 
9 AUX5 
10 auxilary board power control (reserved) 
11AUX6speaker minus
12 U+ tied to +UB, Pin 6 J1

 

 

J3 pins, again 12 pins, starting from the left

J3 socket pin numberUSE                 Notes                                                                                                 
 1AUX13 logic level
 2speaker 2 #1 says plus (notice silk screen reverse polarity of speaker #1, clearly an error)
 3speaker 2 #2 says minus
 4+10 volts really? what for?
 5+5 volts 
 6AUX7 
 7AUX8 
 8AUX9 
9AUX10 
10AUX11 also for SUSI data or servo5
11AUX12 also for SUSI clock or servo 6
12 UVAR regulated DC power common (+) 1.8 v, but can be set by changing resistor 1.5 to 3v

 

So in summary, we need 12 pins on J1, and can get away with 11 pins for J2 and J3... which makes it easy to modify Bachmann adaptor boards sold for.

GP60 motherboard other connectors

 

There are a number of connectors on the mother board.to get the signals and power on and off, below is the legend mapping the silkscreen to functions

 

 connector "number"socket connection silkscreen meaning
X1 - right end (with the silkscreen right side up)  TRKL / TRKRTRacK Left and TRacK Right
X2 - right end  SPK2 SPeaKer 2, note polarity is also on silkscreen
X3 - right end  MOT MOTors, note polarity is also on silkscreen
X10 - right end  +5v / LMPR / AUX7 thru AUX115 volts, LaMP Rear, and AUX 7 through 11.
X12 - right end  SERVO2 / +5v / GND typical servo pins for servo #2
X14 - middle  TRKL / TRKR TRacK Left and TRacK Right (duplicate of X1)
X7 - left end  SPK1 SPeaKer 1, note polarity is also on silkscreen
X8 - left end  MOT MOTors, note polarity is also on silkscreen (duplicate of X3)
X9 - left end  +5v / LMPF / AUX2 thru AUX6 5 volts, LaMP Front, and AUX 2 through 6
X11 - left end  +UB / AUX1 / +5v / AUX13 +UB???, AUX1, +5 volts, AUX13
X13 - left end  SERVO1 / +5v / GND typical servo pins for servo #1

 

 

GP60 Dummy plug notes

Below is a picture of the "dummy plug", shown below (as shipped for DC operation)

Dip Switch labeling/mapping:

Closer inspection shows dip switches apparently mapped to headlights and AUX functions, and the default settings:

The silk screening indicates the 2 headlights (upper left switch position 3&4 and 5&6) and then AUX outputs A1 through A11.

It would seem that only AUX 1 through 7 have something connected. (by the switch positions)

I will verify this, but it's clear there are 2 switches per "output" (normally a led)

So every switch has either: (this indicates what function is controlled)

  • LF or LR (light front, light rear)
  • A1 through A13 for AUX1 through AUX13 (the A is missing on some switches

In addition every switch has:

  • F or R (meaning operation in forward or reverse)
  • ON/OFF (move to ON to enable the desired direction)

Looking at the switch positions as shipped:

  • front light is on only in forwards
  • rear light is on only in reverse
  • the rest are on only in forwards (that is weird)

 

Bachmann / Aristo socket wiring

This is background to help understand the standard socket wiring, since I want to use a Bachmann adaptor plug.

Showing the standards for J1 and J2:

Aristo and Bachmann sockets:

The basic Aristo socket only uses J1 electrically:

 

 Pin #                      J1 function (Aristo)                                 J1 functionfunctionfunction      (Bachmann)        J2 function
 1 Power Pick-up Right SidePower Pick-up Right Side Aux power
 2 Power Pick-up Right SidePower Pick-up Right Side F1
 3 Motor(s) Right SideMotor + F2
 4 Front Lamp Controlrear LED ??? F3
 5 Smoke On/Off*smoke - F4
 6 + Outgnd F5
 7  Ground CommonB+ train bus +
8Smoke On/Off*chufftrain bus -
9Rear Lamp Controlfront LED??SP-
10Motor(s) Left Sidemotor -Reed sw
11Power Pick-up Left Sidepower pickup left sideSP+
12Power Pick-up Left Sidepower pickup left sideXXXXXXXXX                                                                                                                                                                                       
 Aristo did not standardize J2 for power/control purposes
(but sometimes the speaker is wired to it), * Pin 5 & 8 must be bridged for DCC
  

 

 

Comparing the Bachmann standard to the GP60 socket

Casual inspection will show that since J1 pins 1&2 are connected together (to not overload the socket current rating), plugging a decoder so wired into the GP60 would immediately short the 2 rails together, no to mention the connections are completely different.

The Bachmann enhancement of the Aristo socket builds on this standard, and also somewhat standardizes the J2 connector opposite.

So, there is no decoder other than the ESU that will plug into the loco. Please note that the actual implementation in the loco has NOT BEEN VERIFIED as of February 2024.

 

Plan thus far to interface to the GP60

Modify Bachmann adaptor

The Bachmann adaptor has 2 ends, one has 12 pins, but only 10 wires since J1 has pins 1&2 jumpered as well as pins 11&12 (J2 end has all 11 wires needed):

Look carefully at the pictures below and you can see the copper that jumpers these two pairs of pins on J1

 

 

 

 

bachmann adaptor

 

ezgif 5 15f01ba8bc

Modification:

So, we need to slice the large land that jumpers the J1 pins, and then drill 2 holes and solder 2 more wires.

I bought 2 adapters, so I have potentially 4 plugs.

It makes sense to slice the adapters in half so you have 4 independent "plugs". Note the motherboard does not have all the sockets at the same level (crazy!)

 

 

 

 

 

 

 

 

 

 

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