Hi all

Grandpa (my dad) bought my son his first model train this year and we set it up for Christmas.  after a few times around the tree it stopped working.  I checked all the connections and everything was snug.  I noticed the red light on the speed control was not turning on.  I took out my multimeter to try and find the issue.  I read 20V on the power supply.  I tested on the cable termination and on the board of the speed control with the same results (i.e. power is making it to the input on the speed control).  I then checked the continuity on the led light to see if the light was broken and it lit up so that's good.  I also checked the continuity from the track connector (the 3.5 mm  connector) all the way to the track clip and even to the track itself once attached.  This was good.

I've determined that something internal to the speed control has stopped working.  Rather then paying $80 for a replacement to see if that works, i was wondering if there was a circuit diagram available that I could uses to trouble shoot.  I would have assumed the LED light was directly connected to the power in but it seems to not be the case as I tested good power to the board on the input jack but not to the LED.

Any thoughts or preferably design documents would be helpful. 

Thanks,
Peter