Hidden Lighting Feature on Sound Equipped Modern American 4-4-0

[Tom M.]

If you have a Spectrum Modern American 4-4-0 with factory installed full Tsunami Sound, there is a hidden lighting feature you might want to take advantage of.  I have several of these locos and it always bothered me that they do not come with a working backup light on the tender.  In my efforts to install one, I found that the custom Tsunami sound decoder installed in the loco supports the backup light function, but the Bachmann PC board the decoder plugs into does not. 

When you examine the PC board located at the front of the tender frame, you will find connections on the right side marked R+/R-, M+/M-, and a third set marked with just +/-.  The ones marked with R are for the track power pickup and those with M are the motor connections.  The pads marked with just + and – are the headlight connections (blue and white wires, respectively).  However, there is no negative connection pad for the yellow backup light wire.  To take advantage of the Tsunami decoder's backup light function, I simply cut the yellow wire running from the decoder to the 8-pin plug.  The yellow wire was then soldered to a 1K ohm resistor which in turn was attached to the negative lead of an 0602 SMD LED I had installed in a brass backup light casting mounted to the tender deck.  I then took a short length of blue wire and attached it to the LED's positive lead.  The other end of the blue wire was soldered to the lighting function common (+) pad on the Bachmann PC board.

Using this procedure, my locos now have a fully functional backup light.

Tom