Question...

[IndianaChristmas]

A squirrel ate through one of my strings right at the base of an LED.  It is a very nice commercial grade string and it is a sealed unit.  I can't simply remove the LED and replace it.  I have managed to pare away the plastic that encases the remainder of the wires going to the LED. 

Unfortunately, I don't have a "long" lead and a "short" lead to tell me polarity.    Is there a way to identify the polarity of the LED without destroying it?  I can't see the LED as it is inside a cover. I suppose I have a 50% chance of getting it right. 

Thanks.

[chrisatpsu]

are the conductors still intact?  If all that's gone is the plastic, maybe you can re-coat the plastic?

[tbone321]

Unless the voltage on the string exceeds the reverse voltage of the LED, putting it in backwards will not harm the LED, the string simply will not light.  You can also use standard diodes to discover the polarity as well.  I would solder two power LEDs in series (same polarity) and use that to discover the polarity required for the LED.  The reason for two is that power or rectifier diodes have less voltage drop than LEDs and two of them in series increases the voltage drop.  A commercial string should not be pushing the LED forward voltage that close to their limits but diodes are cheap so why take chances.  Power diodes have a much higher reverse voltage capability and will not be harmed by putting them in backwards, the string will simply not light.  When the string does light, then the polarity seen on the diodes is what you will need for the LED.  Make sure to use the same color as the one being replaced to keep the string voltage within spec.

[IndianaChristmas]

Thanks for the input.

The darn animal chewed the wires right off at the hard plastic molded around the wires.  I used a dremel and some careful work to get the plastic removed from about 1/4" of wire so I could resolder to the strand. 

When this is all said and done, it is only one LED.  I suppose it would have been easier just to put the string together with one less LED and not really made all that much difference.

[tbone321]

While this is true for Ican strings for the most part, that is not always true of LED strings.  LED's are very voltage sensitive and depending on the string configuration, removing one LED can cause enough of a voltage increase to kill the rest of the string.

[IndianaChristmas]

I had thought about that as well.  I even thought about soldering an LED of the same color in place of the one that was chewed off.  However, I really don't know the input voltages of the LED's on the string.  How much would it matter if I used one that had slightly higher or lower voltages? I'm not too worried about the new one looking different as I don't think it would really be noticed in  display of thousands of light.
The string was originally a 70 LED string (cool white).  I have some cool white LEDs and I think their forward voltage is somewhere between 2.5-3.3V.  Using one of them probably better than no LED?

[tbone321]

LED forward voltages and voltages drops are fairly standard and dependant on their color.  Replacing the chewed off cool white with one of your cool whites should work just fine.