[Ron Ramirez]

It depends on which ones you ordered.

Do not order any of the real cheap ones, that do not specify that they are usable on AC as well as DC. The ones Mondial and I linked to are fine, and will work on 6.3 volt AC without any modifications. I would not use them on voltages higher than 6.3 volts AC without a dropping resistor, as they are designed for 6.3 volt operation.

Edit: Look for the following in the description of the LED bulbs you are interested in.

These LEDs are AC/DC, meaning they can be used in both controlled (inserts) and uncontrolled (GI lighting) sockets.

Make sure the lights you want have that statement in the description. If you do not see that blurb in the description, then do not buy as they are intended for 6 volt DC only.

In short - The 39 cent LEDs will not work as they are intended for use in DC circuits only. Read the descriptions of the other LED lamps carefully. If the statement I quoted above is not in the description, then I would not try them in an AC application as they probably will not work.