Hi Larry,
I'm not an expert in this but I have looked into it.  I have a 2-8-4 that I want to replace the decoder in with a Tsunami.  All the recent Bachmann steamers I've seen use LEDs for lights.  They require a resistor wired in series with each LED of about 680 ohms, 1/4 watt.  See the Tsunami Installation guide at
http://soundtraxx.com/manuals/tsuinstallation.pdf as it will give you a lot of information.  There were probably resistors on the board that you removed.  I don't know if you damaged the LED's but you might try a resistor and see if it works.
Hope this helps.
Wayne

Has anyone installed a sound decoder in a Bachmann Standard Line 2-8-4?  It would seem you could just unplug the Bachmann decoder, plug in a QSI or Tsunami (with suitable wiring harness),  install a speaker and be ready to go.  Would the capacitors and RF chokes on the Bachmann board have to be disconnected?  Bachman's instructions claim they are OK with any NMRA compatible decoder.  Are there any other precautions necessary?  Thanks,
Wayne32