John, I lost the ability to post to your topic. If at the end you can't resolve this, you can contact me via my e-mail. You could send me just the boards. I can test and possibly repair depending what is happened.
Not sure just taking off is indicating a lost of DCS, though possible. If might be an issue with motor harness leads having a nick grounded to chassis or touching the motor can. The way the motor is powered, if the that occurs it completes the circuit and provides DC power to the motor at full track voltage. Hence why it took off. This could also have been intermitten and the reason the engine was running faster than scale speed. If was periodically getting straight DC.
I would examine your motor harness, in fact pull the motor lead plug and see if that restores sounds and lights. If not see if you can readd the sound file with the motor plug removed. You really only need the 7 pin power plug installed to add the sound file. G
