My wife's reading lamp failed. I replaced the 100W 120V halogen bulb, which did no good so I pulled out the dimmer circuit. I know nothing about these but after googling for light dimmer I found this:
The "typical 120V AC dimmer circuit" uses almost the same components that are on my dimmer: two diodes cap resistor pot diac triac
The diodes test good one way so I wonder if either the BT137F triac or the DB3 diac are the problem. Can these be tested with a VOM?