After splicing, replacing, shortening, enlarging these pieces of CHINA CRAP thatpromise great hours per dollar and savings...... well here is the real fix friends. > When ALL of the above fails, REPLACE the transistor (or capacitor?) inside the plastic "tubes" by cutting such encasing.
FIRST RE SOLDER those> Bad Chinese materials> (even if your tester says it works fine> TRY IT ON THE ACTUAL light strands the way it was installed. New ones are cheap, specially online. Re-solder or replace, then RE ENCASE the whole thing. You can use a hose like the ones used for small water lines in landscaping. Put A LOT of tape (duct, electrical?) INSERT THE LITTLE HOSE FIRST in one end of your wire, so you don't have to splice it lengthwise again to insert the repaired/or replaced transistor.
On my C7 (70 lights) is a grey or light blue with 2 red lines (I think)
Do this AFTER trying the bulb AND fuse repairs first> VOILA!!!! your lights shine again my friends.
Merry Christmas to y'all from sunny Newport Beach, Balboa Peninsula, California. 2015