Dell B130. display is dim, can't get display even on a external monitor

It would most likely be an issue with the graphics but I will suggest disassembling and cleaning the laptop (if it hasn't been done) as a first step - it may simply be a lack of air flow over and subsequent cooling of, the integrated graphics is causing it to strain.
Are you sure the external monitor isn't too much for the laptop's graphics? It's not a 1440p 1ms monitor or anything too elaborate is it?