Archive for November 25th, 2017

Compact Fluorescent Bulb Autopsy

I fished the failed CFL bulb from the recycling box:

Failed CFL - case damage

Failed CFL – case damage

The straight-ish crack between the tube ends looks like it happened as the (yellowed) plastic ruptured and hardened.

Not wanting to get a face full of glass fragments spiced with metallic mercury, I wrapped a blast shield around the spiral tube:

Failed CFL - tube wrap - shattered base

Failed CFL – tube wrap – shattered base

The terminal ends fit loosely in the crumbling base at the start of this operation, leaving the tube wobbling above the base. The plastic cracked as I wrapped the tube, so, for lack of anything smarter, I applied a pin punch to break away the rest of the upper base.

The tube doesn’t fit into a socket, of course, and terminates in four wire connections:

Failed CFL - tube terminals

Failed CFL – tube terminals

Those wires pass through notches on the edge of the PCB, bend around the board, pass through vias, and get soldered to pads. The solder side faces the tube, with all the components nestled into the base toward the screw terminals:

Failed CFL - PCB solder side faces upward

Failed CFL – PCB solder side faces upward

The component side sports a surprising number of parts:

Failed CFL - PCB components - 2

Failed CFL – PCB components – 2

A view from the other direction, where you can see the tube wires curling around the edge:

Failed CFL - PCB components - 1

Failed CFL – PCB components – 1

I generally harvest inductors & suchlike, but it got really really hot in there and, methinks, cooked the life out of the parts:

Failed CFL - overheated capacitor

Failed CFL – overheated capacitor

The PCB date code stamp could be “730”, suggesting either 1997 or 2007. In any event, it’s been a while.

I hope LED bulbs outlast these things, but I have my doubts …