This will sound odd. I have a lamp I got from a friend that powers a low wattage 12v 20w bi- pin bulb. The wiring they used is SPT-1 which is good for up to 300v. The end of the plug is a polarized set of pins that looks like it went into a transformer.
My question is this: Can I change the end of the wire to the north american 120v standard end and just use a 120v 20w bi- pin bulb in the current bulb housing?
Here is a picture of the bi- pin bulb type I am talking about
There are many things to consider here !
As the standards for a 12v lamp would be much lower
than that for a 120v lamp.
Are you real sure the cable is safe for 120v operation ?,
How good is the isulation, will it damage or melt easily ?
How is the cord secured, is it well isulated from metal ?
If you really want to use lamp at 120v,
remove the old cord and replace it with one,
you know for sure is safe at 120v.
Better still get an electricain to do it, or at least check it !
I would say unless the lamp was built for 120V, its a bad idea to convert it. For example, the two-pin base bulbs can be a much higher wattage, so if someone after you puts in a two-pin 100w bulb, it could cause a fire if the reflector or insulator is not made for that.
Note that cheap manufacturers do things like use cardboard as an insulator...