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Fuse Resistors, CFLs, and God Awful SMPSes

  1. Apr 3, 2009 #1
    The other day I came into my living room, and noticed that the CFL in one of my lamps was flickering like crazy. Of course having a propensity to possibly fatal curiosity as some humans do, I walk over and grab the base to see if maybe the bulb isn't seated properly. The base of the bulb is scorching hot! A second later, the bulb starts smoking. I quickly pull the plug and disaster is averted. After calming down for a minute and nursing my burnt thumb, I decide to pop the bulb open to see what could have happened. The inside of the bulb is melted and charred, but on the ground lead of the wires leading to the switching power supply is what looks like the melted remnants of a wire-wound resistor, still stubbornly holding itself together across the line. Probably a transistor in the supply gave up the ghost and caused a short, but I wondered to myself just how long this "resistor-fuse" would have drawn short circuit current? Until it caught fire, I'm guessing. I'm not even sure the manufacturer used a proper resistor fuse, it could have just been an ordinary resistor for all I know!

    A few days later, I had an ATX power supply fail - it couldn't provide any current on the 5 volt standby line. Thinking it might be an easy fix I opened up the power supply, and the soldering job is the biggest mess I've ever seen. On the underside of the board it looks like some of the main ground buses were too resistive or something, because the manufacturer has taken big pieces of bare jumper wire and slapped them on top of the ground buses and tacked them in place with big blobs of solder. :eek: Half the joints on the board look cold, though this could just be a side effect of it being "RoHS" compliant the job really looks awful. And of course a big ol' resistor on the primary side where on other supplies there is a proper fuse. And this is in a supply from a supposedly high quality "boutique" manufacturer that cost nearly $100. :yuck:

    The lesson learned is that I don't leave my house with SMPSes running anymore. :frown:
     
  2. jcsd
  3. Apr 3, 2009 #2

    berkeman

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    Staff: Mentor

    Yikes, the CFL (compact flourescent lamp) ballast story is downright scary. Who was the manufacturer of the light fixture with the ballast? Who made the ballast, can you tell?
     
  4. Apr 4, 2009 #3
    I will try to get some photos up when I get home after the weekend.
     
  5. Apr 6, 2009 #4

    dlgoff

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    Science Advisor
    Gold Member

    This really worries me.
    http://www.city.quintewest.on.ca/services/fire/prevention.htm" [Broken]
    Here's a picture of what could happen:
    BurntBulb3.jpg
     
    Last edited by a moderator: May 4, 2017
  6. Apr 7, 2009 #5
    I have had a similar thing with a new CFL. It had started smoking on me and then the base plastic started melting and turning black like it was on fire. I immediately switched the circuit off - makes me wonder about the quality of these things. Maybe I'll keep using incandescents - saves me money from running the gas furnace :)
     
  7. Apr 7, 2009 #6
    maybe what we need here are some space-age flame-resistant ceramic bases.
     
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