Help Identifying this part?

Discussion in 'General Electronics Chat' started by dpresley58, Jan 23, 2012.

  1. dpresley58

    Thread Starter New Member

    Sep 1, 2009
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    0
    Can anyone help identify this part? Its on a torch lamp (the tall decorative ones). This particular lamp has an incandescent light on top and a halogen about midway down. The part shown here is wired directly to the mains cable, I -think- on the hot side, going to the incandescent. When I turn the pot switch/dimmer on, the light comes on briefly and then fades out. The fade takes about a second or so, and then this part is pretty hot.

    It looks like some sort of capacitor, but the markings on it are strange to me. Two lines:

    WH130
    1350

    ...and thats it. Any insight would be helpful.

    Thanks
     
  2. debe

    Well-Known Member

    Sep 21, 2010
    946
    184
    Suspect its a PTC, positive temp coefficient resistor/Polyswitch protector, going by the numbers its a 130V @ 1.35 Amp. Used to switch an excessive load of by heating up, then self reseting when cooling down. This picture is of one out of a 24V 4A powersuply.
     
  3. evilclem

    Member

    Dec 20, 2011
    118
    16
    I agree with the polyswitch (PPTC) suggestion, commonly known as a resettable fuse.

    If the unit draws too much current then it heats up. At a certain current point the heat builds up rapidly causing the device resistance to increase. The high resistance reduces current to a safe level through the lamp, when power is removed it cools down and the resistance drops.

    Perhaps the bulb is rated too high for the lamp.
     
  4. dpresley58

    Thread Starter New Member

    Sep 1, 2009
    7
    0
    Ohhh! So, this part is only doing its -job-! Thanks for the help. It lets me know I have to look further for the actual problem. I'll take a look at the bulb. It'd be great if the solution is as simple as that.
    I was going on the assumption that any part heating up to that extreme was faulty.

    If I'm understanding your replies, the problem is on the load side, i.e. the bulb. Can I assume that if the bulb is the correct rating that possibly something in the circuit has failed and is supplying less current than it is supposed to? Would the PPTC still kick in under those conditions?
     
    Last edited: Jan 24, 2012
  5. debe

    Well-Known Member

    Sep 21, 2010
    946
    184
    If the load is correct then the part wont get that hot. Its only realy hot in shutdown mode.
     
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,779
    932
    A loose connection(or an oxidized, corroded one) will generate lots of heat when current is pushed through it. Check everywhere there is a change in conductor, or a connection is made.
    The description sounds as if you have a partial short(a resistive connection) in your lamp. The lamp works properly, but the added current being pulled by the partial short is causing the protection fuse to operate. One way to check this would be to plug it into one of those watt-meter devices they sell for tracking electricity usage. Or by using an ampmeter. Incandescent lamps use about 1 amp @ 120vac per 100 watts. Halogens just slightly less than that.
     
  7. dpresley58

    Thread Starter New Member

    Sep 1, 2009
    7
    0
    Two 60w bulbs are being used. The sticker on the light socket warns against exceeding 130w total. I'm going to try a few things: reducing the load to 2-40w bulbs and looking through the circuit board for loose/corroded solder joints. I'll also try seeing what kind of current is running up to the incandescents.

    If anyone has any insight in the meantime, it'd be appreciated.
     
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