Attempting to add backup light to run a Bachmann On30 Shay on DC. Bachmann PCB has contacts for LED 1 and LED 2; the latter is used for the headlight, which, when run on DC,  lights with the engine going forward but turns off in reverse. Connecting an LED to contact 1 gets no response, in forward or reverse. (Yes, I tried polarity both ways.) Adding a SoundTraxx 8 pin Pn'P decoder, the DSD B2TS, gives sound, but still no solder pads for backup light. Connecting to pins 2 and 7 should do it, but I'm not sure I can solder to such a small spot without destroying the no-longer-available decoder. Anyone have any suggestions?  Thanks