I had just posted to the thread about end of 100 W bulbs, but realize that my concern about Christmas light strings fits well here and deserves a new topic. I still use my old old mini series christmas light strings. I have usually been able to detect failed bulb positions with those cheap inductive lamp detectors or with a volt meter connected to ground and a section of the non-lit string.

It doesn't appear that failed light sections can be tested with LED string lights. Of course they claim that they won't burn out, but that is essentially false. The bulbs can get slightly dislodged, and especially if outside, the contacts can get corroded.

My current example: we had two of those old lit mechanical dear. After 11 years of casual bulb replacements and not always replacing every unlit (but shorted to maintain the circuit) bulb, I finally overloaded them into oblivian. If I had replaced every unlit bulb, they would probably be running like most of my other 20 to 30 year old light sets. So we bought a new dear with those UG-LY garish lights and the set shut down while setting it up. I found that my old testing methods wouldn't work, but while fooling around, I banged into the loose bulb and all was well for the first year. But last year, it wouldn't light and now I have a dead useless piece of crap. I assume if I had considered replacing my old strings for the planets good, that especially for outside lights, they would all be dead in two or three years. Is there a solution?