I have been trying to put a complete roller assembly on an F3. I replaced the unit and wired it the same as the old one. However when I put the loco on the test track it sits there and then the z 750 shuts itself down. I then took the truck itself off the frame and put on the track and it shorts out the transformer again. I put the old roller unit back on and the same thing happens again. What am I doing wrong and what should I be looking for? The loco did run, not well before I started which was why I am changing the roller assembly and now it doesn't run at all. Thanks in advance for any help
Bruce C
