S Helper F-7 TMCC Compatible Conversion
Using the Electric RR Co's Mini Commander and Sound Commander

S Helper Services F7

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With this conversion I  wanted to keep the   loco's original factory wiring etc. and make it a plug in adaptation. The only thing to do was to replace the factory plug in board with my adapter interface board and tape the new TMCC compatible boards down.  
In a  previous conversion the SHS F3 A and B units had the sound unit in the B unit.

 With this conversion I need sound unit in the A unit. Space was a concern because of the crew's cab but it fit with some careful planning and a bit of luck .   
The plug in interface board is key to the ease of the conversion. It was made with a piece of vector board and a mating header connector. The board has the motor rectifiers, dropping resistors for the bulbs to keep them cool and a rectifier for the classification LEDs.
Careful placement and orientation of the boards was need to clear the shell. The boards are held in place with double sided foam tape.

The Sounds include Prime Mover stepped with the throttle, Air Brake pop offs, Horn and Bell
This is the layout of the interface board. Note the filter capacitor is on the bottom side of the board.

Program to engine type 5 and Aux1-8&9 (LC-2) will control the mars head light.

The header connector is a Mouser part number 575-641001.

This is version is for single headlight locos.

Program to engine type 6 and Aux1-8&9 (LC-2) will control the number board lights.

TMCC Compatible conversion of SHS's F3 uses the Electric RR Co's Mini Commander and Sound Commander boards. These are the only TMCC compatible systems that will fit. 

These Mini Commanders have a my custom version of firmware to allow engine functionality.  It was set to an engine type 5 so the mars light flashes

The wiring diagram shows the interface board header pin numbers.