Electrical Puzzle?

[Julie]

I have a lamp I am trying to fix.

It's a 3-pendant floor lamp, and it came with a slider (dimmer) box between the plug and the light. I heard a "pop" the other day, and the lights went out. Today I opened up the box, and there was a circuit board inside. On the board is a slider/resister, a few other componenets, and (I think) a transformer attached to a heat sink.

The pendants take 120V bulbs, so I expected I could take out the dimmer board - cap the wires together (2 #14s), and revert to a normal lamp. So I did that, and ...

only one of the three pendants lights up. Eh?

Trying to remember assembling the lamp - I'm pretty sure it was wired straight through - ie, no switches or junctions inside the fixture, at least that were accessible to me.

Any ideas?

JSH

[John Grabowski]

Julie, Did you try replacing the bulbs?

[RBM]

[Julie]

"John Grabowski" wrote

A-ha. Nope! 'Course that was it, and here I was trying to come up with a circuits-101 final exam question ;-).

There was a blown fuse on the board, so I'd imagine when that blew, it must have taken 2 of the bulbs with it. Good thing it didn't take all

3, since it clearly would never have occurred to me to try new bulbs!

Thanks.

JSH, feeling rather dim.

fixture, at

[Joseph Meehan]

More likely one lamp blew and that knocked out the dimmer. As for the other lamp, maybe it has been out and you did not notice.

[trader4]

And why did Julie re-wire the dimmer box and eliminate it instead of just replacing the blown fuse in it, which likely blew when the one bulb failed?

[Chris Lewis]

According to Julie :

Consider yourself lucky. Semi-conductor dimmers usually fry themselves faster than a bulb or fuse can. If the dimmer had more than just a "slider resistor" it's probably a semi-conductor dimmer (like a wall dimmer using a SCR or Triac).

Likely one of the bulbs died by shorting out. Moderately common failure mode, usually doesn't do anything bad unless there's a very sensitive and _fast_ circuit overload device in the way.

Like a semiconductor switch (SCR or Triac)...

When I hear "pop" from a wall dimmer, it always means I have to buy a new one.

[Julie]

wrote

1) The lights are fairly dim already, and the dimmer switch, on the cord, is about a foot away from the light's base - between these two, I never, ever touched it. 2) Some genius soldered the fuse onto the board, and I didn't feel like bringing it into work to re-solder a new fuse in, and probably needing to repeat that in another six months.

JSH