I have never seen light strings with fuses in the plugs will have to look again, but what we DO have is light strings with "Fusible Links". These strings may well have more than two light series in them, separated by a fusible link on each end of the series. Imagine a ladder where the legs of the ladder represent each side of a 110 volt circuit. The light strand(s) are the rungs with perhaps 20 lights per strand. At the intersection of the "legs" and "rungs" you have a fusible link. If a short or a break occurs in any of the light strands, one or both of the fusible links will blow, are sealed for life, and are not serviceable. That light strand will be out and the rest of the strands will remain lit. The fusible links are for safety, not for convenience.
Now for a bit more info. If you try to cut out the fusible links or even replace them with a more serviceable unit, you need to understand something about LED's as opposed to incandescent lights. LED's operate on Direct Current (DC) and will only light with that current running in one direction. They would blow up (literally) if applied to 110 volts AC when they are designed for more like 6 volts DC. So in every light base, or as part of the fusible link, there will be another diode whose job it is to create that DC low voltage. To remove that is to invite disaster.
If you have a string failure, best to cut your losses and go get yourself a new one.
This isn't the same thing as testing for bad lights and replacing them. This is quite different. Meantime, I'm gonna keep my eyes open for those one with replaceable fuses.....
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I don't see that chris mentioned a single light as being a problem....
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As to the fix you mentioned, if there are that many disposed light strings, could you not cut that light out and replace it with a salvaged one. Might be the best solution as these strings are in series. Every light removed increases the amperage of that one string. This will case other failures eventually. The diodes on these things are balanced with the deign load. They do have a "Threshold" that once exceeded will fail, then that whole string will be out.
I have never seen light strings with fuses in the plugs will have to look again, but what we DO have is light strings with "Fusible Links". These strings may well have more than two light series in them, separated by a fusible link on each end of the series. Imagine a ladder where the legs of the ladder represent each side of a 110 volt circuit. The light strand(s) are the rungs with perhaps 20 lights per strand. At the intersection of the "legs" and "rungs" you have a fusible link. If a short or a break occurs in any of the light strands, one or both of the fusible links will blow, are sealed for life, and are not serviceable. That light strand will be out and the rest of the strands will remain lit. The fusible links are for safety, not for convenience.
Now for a bit more info. If you try to cut out the fusible links or even replace them with a more serviceable unit, you need to understand something about LED's as opposed to incandescent lights. LED's operate on Direct Current (DC) and will only light with that current running in one direction. They would blow up (literally) if applied to 110 volts AC when they are designed for more like 6 volts DC. So in every light base, or as part of the fusible link, there will be another diode whose job it is to create that DC low voltage. To remove that is to invite disaster.
If you have a string failure, best to cut your losses and go get yourself a new one.
This isn't the same thing as testing for bad lights and replacing them. This is quite different. Meantime, I'm gonna keep my eyes open for those one with replaceable fuses.....