Range hood lights won't work

I have a toche Range hood that requires 2 - 10w halogen bulbs. At one point, one of them was replaced with a 20w, now neither will work. The bulbs are still good. What did I fry? Inside there are two covered boxed wired together and attache to the lights, tho they do not light independently.
Are these ballasts? transformers? Our ohm meter does not fit into the tiny pin slots for the bulbs, or the socket attachments for the bulb bases. What do I do?