I have a string of 150 christmas lights. The middle 50 work, but the rest aren’t working.
I found 2 missing bulbs which I replaced, still no luck. I replaced the fuses too, but the problem persists.
Surely I can’t have 100 burned out light bulbs, I just got the lights.
It doesn’t make sense.
Does any one know where the problem may be?
I think I fixed one part. Sort of. I tested each non-working bulb by inserting each into one of the light sockets in the working section. # 1(first from prong end), 15, 49(last of the 1st non-working section) – 57 and 98 were not working so I replaced them. When I replaced #15 (this was the last light I replaced), the first half of the string started working, but because, by then, I was using the light bulbs from another set of spares (from different lights), the bulb would dim in and out and cause that part (first 1/3) of the string flash on and off. The box says “steady illuminating bulbs remain lit even if one goes out”. Right.
You don’t tell us if the light string are the filament type bulb or the newer LED lights. But if the string has the old filament type bulbs, it would be better to just shitcan them and buy a set of LED lights. I used to fight with the same problem as you are experiencing. LEDS stopped that problem. Moreover, if you’re putting the lights on a real tree instead of the ersatz plastic thingy, LEDS never get hot and dry out pine needles. That’s a comforting feature knowing you not likely to burn the house down. LEDS were fairly expensive when they first came out, but I’ve seen them this year for less than 15.00 for a string of 100.
I’ve no idea if any of this helps, but there you go.
My lights are the old incandescent bulbs. I prefer this type because I think they have a warmer/softer glow to them than LEDs.
Thanks for the pointer, tent. I have a live tree and it already has 400 incandescent lights on it. 
Maybe I’ll give them a try next year.
Thanks tent.