I'm working on 150 led light set right now . So far found the string is broken up into 5 sets of 30 each. Two fuses are in the plug going to the outlet. No mater which way arange them, if both are not in,none of them work, so I would say the whole string is dependent on both. The led bulbs are polarized, so they will work in one direction. There are two leads. The long one is positive. On my string I ave to insert the new bulb with the long lead towards the tab or latch, and this will have to g in the right direction. Still haven't figured out the problem with a middle section yet.using a voltage detector to find a pattern. There is a small tube device for each set of 30. Anyone know what this.