Do you mean one of these?

Here is a link that might be useful: String light remover

PM, I used one of those Pros to fix a set of 10 icicle lights and afterwards, they got so hot, it melted the icicles.
I tried to use it to fix some of my other mini lights and it did not work.
It does work well to test bulbs and remove them from strands, so if you are willing to go through and test bulb by bulb, often there are multiple bulbs causing the mini lights to not work.

JMHO,
Candy

I just got one for my LED lights. Yesterday it worked for one string, but not for a second string. I'll try a third string tonight. When I take the outside lights down, I'll try it on the two strings that are half out (I shoved the unlit portion down into the bushes) and if they all work, the Pro will have paid for itself, and everything else will be "gravy".

It's a little tedious and sometimes confusing/frustrating to go through the string, but if it fixes it, you feel better :)

I bought one for my hubby after Christmas last yr ...he tried to use it on a long strand of outdoor lights ...still had the tedious work of going thru the whole string taking each bulb out one-by-one ...he finally gave up & put up another strand ... so I don't know, party ... sounds like a 50-50 deal on this Pro tool. Jeanne S.

Thank you all for the replies!

OA, I checked the link you gave and read how they are used. I really didn't know anything about what they could do or how they did it.

Candy, thanks for relaying your experiences. With my bad luck I tend to get the worst result, so it doesn't sound promising for me. lol!

bpathome, I have the 'half string' syndrome going on here too. I tried every string and only put up strings where every bulb was working. Once they were up they decided that half of some strings should not work -- these strings are both inside and outside. :p

Jeanne, it does sound tedious, and I'd probably give up on the whole thing quickly if it doesn't always work.

Thanks for the info everyone!