I have a Hampton Bay ceiling fan with lights. The model # is 52-RDT. The lights have a socket that will only accommadate 40 watt bulb with a small (Chandalier) base. Is there such a thing a 40 watt RD20 bulb (directional) with a small (chandalier) base? Where can I find it? None of the box stores including Home Depot have them, even lighting specialty shops don't have such a thing.

Search the internet... if it doesn't exist there it doesn't exist...

Please take one of the working bulbs and place it in the failing socket. If the blub works then you need to find either a replacement blub or change out the light pack.

If the blub fails, then you need to check the wiring on the socket looking for loose connections and possibility the tab at the base of the socket has been bent down and not making contact with the base of the bulb.