by BJF » Tue Sep 16, 2008 7:35 am
Hi,
If you can't tell polarity on the LED's, and yes most have a longer leg for their positive side-the anode, another indicator is that inside the bulb the smaller part is the anode and the larger part cathode. This can be hard to see depending on the bulb.
If you have a DVM you can diode measure them and then one should light at a time: you take one probe to the end on the pcb where all of these clipping elements join and the other probe to ground.
Note that if one or both LED's are shorted then none will light up. This can be resistans measured with a DVM and power prefeably off from circuit.
At your service
BJ