my particular LED's operate on AC (noticeable strobe/flicker in peripheral vision much like an old CRT tv)
I looked at the strand and actually pulled an LED out, and there is in fact, no diode. There is also no in-line box or anything indicative of additional in-line electronics. They also pass 120V AC to the next strand (and in my case, through 10 strands) because they power small incandescent mini light globes at the end.
A friend of mine just put up all his led strands and low and behold there are at least 3 or 4 sets out of 15 that are completely dead. They worked last year and were stored indoors, not abused or damaged.