How do I remove top of boiler on 2-6-6-2. I removed top center screw but still cannot get shell removed. I installed tsunami today and front  led blew out with resister installed. Apparently the light is being powered by another sorce inside. When you install this decoder the front light goes to white, the rear to yellow and the blue is common. I just want to get inside to change & isolate light  if necessary. Regards  Mark