TMCC Compatible DC Driver Board 
Mini Halfwave DC Driver Board

Lionel's TMCC system's receiver current design is too large for installation in some AF engines. The original LCRU design would fit in the AF Geeps  with heatsink modification but that unit is no longer available.  Digital Dynamics AC/DC DLX will fit in most AF tenders but will not fit into the AF Geep and smaller tenders.  The receiver (R2LC) made today has been modularized and is separate from the motor driver board, Railsound board, and Mother board.

 I have designed a no frills half wave DC motor driver board to fit in a much smaller space than even the old LCRU design. This design is suitable for most DC can motors up to 4 amps. This page will present this design as a possibility if the modeler has a little skill with the soldering iron.

Drawings and Schematics and Parts list available here. It uses common parts and should be able to be built for about $10 for the components not including the R2LC receiver board.

If you have any questions or Comments or Ideas drop me a line at

Click image for larger view.

Comparing sizes between the  current style on the right, older original version in the middle and my own mini board with the R2LC receiver piggybacked on the left.


This is the prototype Mini Driver board. For a printed Circuit board that can be made instead (see below)


It is a prototype.  Heat sink is electrically isolated from SCRs with mica insulator and plastic washer. The board assembly uses the heatsink for mounting to the chassis also. It is  a piece of 1/16" aluminum 1" wide X 2" long bent into an "L" with holes drilled for the SCRs and amounting screw hole on the bottom of the "L" 

The Lionel R2LC receiver on the left plugs into the mini driver board on the right

Width less than an inch.


Length just shy of two inches


Height one and a quarter inch.


Testing it ... It works!


This is the Schematic of the Mini DC Driver Board. Not much to it. 
Note the use of a 100uh RF choke in the return side of the Track voltage. This is used for Two rail operation.  All return leads of bulbs and smoke unit need to go to the Terminal number 3 also.


This is an X-ray View of  PC board design

For a list of parts and PC board Design CLICK HERE

R2LC Receiver Pinouts

1,2  -    AC Hot Center rail on 3 rail track)
3,4  -    AC Return (outside rail on 3 rail track)
5,6  -    Smoke output
7,8  -    Rear coupler
9,10 -   Rear headlight
11,12 - Front coupler
13,14 - Front headlight
15 -       i/o2 (-4 only)
16 -       Reverse motor drive
17 -       i/o input (from smoke switch)
18 -       Forward motor drive
19,20 - +5 volts out (30ma max)
21 -       Master Clear to microprocessor
22 -       Program/Run switch input
23 -       Antenna
24 -       Serial data out (Railsounds)