I have a 7 ft. G.E. Trim a Tree 11 (0329202). The top section of lights went out. I replaced the fuses in the plug but it still doesn't work. All of the lights pull out except one which does not have the little collar around it. It has white what looks like insulation on the inside of the holder and no collar but it looks like it is the one that is burnt out. How do I get it out and why is it different from the others?