I recently was given two strings of LED blue/white Christmas lights.
The bulbes are in series, with 35 lights in each string. There are
also a couple of lumps in the series lines. They appear to be just
resistors, not diodes, as I measure the same value (~500 ohms) with
either polarity of my multimeter. My guess is that the resistors are
there just to decrease the current so that the LEDs are not running
overrrated. I am thinking of putting/rewiring the two strings
directly in series and then reducing the series resistors until I get
the same overall brightness of the new 70-light string. Has anyone
done any experimenting like this?