Can someone help me identify this bulb?

Discussion in 'General Electronics Chat' started by stormBytes, Sep 3, 2015.

  1. stormBytes

    Thread Starter Active Member

    Jan 26, 2010
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    I pulled this from a nightlight, the kind that plugs into a wall outlet. I didn't really troubleshoot it part by part; I'm assuming its a bad bulb only there's some leftover solder on parts of the bulb and I can't make out what it is so help would be appreciated. The new variety are all LED and well, my mom prefers the incandescent. Thanks!
     
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  2. RodneyB

    Active Member

    Apr 28, 2012
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    It Looks like the lamp used in a vehicles curtesy light.
     
  3. elec_mech

    Senior Member

    Nov 12, 2008
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    Looks like a mini bayonet base. To check the bulb, use a multimeter set to measure resistance and put one probe on the tip at the bottom and one on the metal side. A good bulb should have a very low resistance. A bad bulb will show an open, much like a blown fuse.

    Assuming the nightlight is providing 120VAC directly to the bulb, take a look at Batteries Plus or here. While it will cost some more, you should be able to find a Batteries Plus store close to you and verify the size and fit is right. The second link has a video showing how to verify the size is correct with a pair of calipers.
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    I see what looks like 60 and 4W
     
  5. Marcus2012

    Member

    Feb 22, 2015
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    Looks like it might be a BA9s bayonet cap type. Automotive bulb basically for older cars, not entirely sure though without the dimensions to hand. T4W might do the trick, if not then there are some with the BA9s cap and a narrower head.
     
  6. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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  7. stormBytes

    Thread Starter Active Member

    Jan 26, 2010
    41
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    I see the bayonet and automotive definitely makes sense. I can also make out the "4w" part, its the "60??" that's throwing me for a curve, especially since its an a/c nightlight. I'm guessing the voltage is stepped down from 120AC (resistors) and half-rectification el-cheapo style (see circuit pic) so my plan was to plug it into the mains, as is, and measure output voltage on the bare leads.
     
  8. Marcus2012

    Member

    Feb 22, 2015
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    Think Dave's right on the money with that one

    EDIT: Actually the one in that shop seems a lot longer than yours
     
  9. Marcus2012

    Member

    Feb 22, 2015
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    This one is it I think

    Miniature bulb 60v 4w ba9s t10x28

    edited for American supplier

    One thing though make sure that it definitely says "60V4W" on the bulb and not "60V2.4W" The solder might be hiding it I can't make it out
     
    Last edited: Sep 3, 2015
  10. stormBytes

    Thread Starter Active Member

    Jan 26, 2010
    41
    1
    Wow nice catch! I'm gonna have to see if i can get some of that solder off (wish i had a wick!)

    And good call on the 2.4 --- I noticed it didn't seem to see 60V4W, theres some extra character there I couldn't quite make out.

    All in all it seems like it would make more financial sense to just buy a new nightlight but.... i rarely make financial sense!

    ps: anything specific I might look for in a soldering wick/braid?
     
  11. Marcus2012

    Member

    Feb 22, 2015
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    Yeah I saw the 2.4W ones for sale and it clicked that it might be under there :). As for wick, generally the finer the wick the better the capillary action and some people swear by flux-impregnated wick and it is good but more expensive. You generally get what you pay for but I get by with cheap wick and apply flux as needed.
     
  12. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Looks like an Ne51 (neon mini bayonet) bulb.
     
  13. Marcus2012

    Member

    Feb 22, 2015
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    I'm pretty sure its a normal filament bulb but I did think that originally because the light reflection looks like a tube :)
     
  14. RichardO

    Well-Known Member

    May 4, 2013
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    I like this theory because of the "60V" part of the number. If it is a neon bulb there will be a large value resistor (a few hundred kohms?) in series with it and no other components.
     
  15. Marcus2012

    Member

    Feb 22, 2015
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    Think it's a step down converter and the unwanted voltage is dropped across the capacitor and that 2.5M resistor is a bleeder resistor, but I am totally unsure though as I can't see the traces.
     
  16. RichardO

    Well-Known Member

    May 4, 2013
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    Oops. I should have looked at the pictures -- there are other components...
     
  17. ian field

    Distinguished Member

    Oct 27, 2012
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    That's what it looks like to me as well, and the small bayonet cap they used to use in dashboard clocks - not the bigger size used for side lights.

    Not sure what uses 60V though, telecoms use mostly 48V and avionics is usually 28V.
     
  18. stormBytes

    Thread Starter Active Member

    Jan 26, 2010
    41
    1
    Ordered some desoldering wick. Should be here by tomorrow. Then (hopefully) the mystery of the hidden lettering will be unravelled at last!
     
  19. stormBytes

    Thread Starter Active Member

    Jan 26, 2010
    41
    1

    Traces.
     
  20. Marcus2012

    Member

    Feb 22, 2015
    349
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    Doubt there's anything wrong with the PCB here and it just looks like a half wave rectifier like you said and a LDR/BJT switch, so it should work like..

    Vmax = 120Vrms*1.414 = 169.68V

    169.68/Pi = 54.01VDC equivalent

    Just make sure that bulb is the right wattage :) Think it is 2.4W though, that's what my money's on :)
     
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