Why are Touch Lamps so fragile

Discussion in 'General Electronics Chat' started by Gdrumm, Dec 16, 2010.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Twice now I've had visitors accidently knock a small touch lamp onto the floor; and twice, it's broken the "touch feature" of the lamp.

    Fortunately I've been able to go to Home Depot and buy / replace the little box (board) that makes it work.

    But I'm just curious, what part of that board is so fragile that knocking it off the table (with a 2 feet drop onto a carpet covered floor) kills it?

    I've tried testing the thing for bad components, and I just don't have the knowledge.

    What might be failing due to a mild shock like that?

    Gary
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Have you gotten the same brand of lamp each time for replacement?

    If the board isn't mounted solid, it could be shorting against the metal of the lamp or something along those lines. I am assuming the lamp has been plugged in at the time it was knocked over?

    I doubt static electricity would destroy the board, as they are designed to withstand ESD due to the metal contact interface for operation.

    Can you post a well lit, clear and focused picture of both sides of the (broken) circuit board(s)?
     
  3. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I should have specified, it was two different lamps, not the same lamp twice.

    I'll have to get my camera from work tomorrow to take pics.

    Thanks,
    Gary
     
  4. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Aren't touch lamps just begging to be knocked over?
     
  5. sceadwian

    New Member

    Jun 1, 2009
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    It's probably dirt cheap Chinese made junk. You probably fractured half the solder joints on the board when it hit the floor.
     
  6. debe

    Well-Known Member

    Sep 21, 2010
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    One posabillity is when its knocked over the bulb has internaly shorted &destroyed the Triac in the module.
     
  7. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I am surprised that THD has replacement parts.
     
  8. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    The Triac might be the culpret, but the last lamp that got knocked over stuck in the on position, and would not turn off.

    The first lamp that got knocked over would not turn on.

    Does sound like the triac (could it's failure have produced both of those outcomes), or is it more likely seperate issues for each lamp?
     
  9. debe

    Well-Known Member

    Sep 21, 2010
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    If it wont turn off it would be a safe bet the Triac is shorted.
     
  10. retched

    AAC Fanatic!

    Dec 5, 2009
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    Maybe its not Scottish.

    And as we all know, If its not Scottish...:
     
  11. Wendy

    Moderator

    Mar 24, 2008
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    I don't know, what about Scottish?

    Don't wear kilts if you're not Scottish, because then their dresses? :D

    Back on topic, I assume you've inspected the boards closely?
     
  12. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Sorry for the delay.
    The Triac looks cloudy on it's face, but is still legible.
    It is a BT135 6005 (may be 600S) Phm 0022 E1

    I looked on Digikey, they don't have a BT 135, but I found a BT136, 600D, 127, with the following specs:
    600v 4A, TO220 AB, Logic Sensitive Gate, Through Hole, Single.
    10mA current hold, 600 Voltage off state, 5mA current gate trigger,
    current non rep. surge 50,60 hz, current on state RMS max 8A
    Voltage gate Trigger 1.5 volts, at a cost of 95 cents each.

    Does that sound like a suitable substitute?

    Thanks,
    Gary
     
  13. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I found out by closer examination that it is a BT136.

    Datasheet has all the details, and it appears to be a common one.

    I should be able to find one pretty easy.

    Thanks,
    Gary
     
  14. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    It may not be the Triac that failed.

    Can you post a photo of both sides of the board you are looking at? It could be something entirely different, even a cracked PCB or broken solder joint as mentioned above.

    Do you have a DMM?
     
  15. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I do have a DMM, but I also have an Analog Meter.
    I used the Analog and set it on 1x, and checked the Triac, it seems to check out okay (using test procedures I found on the internet).

    The board looks solid, and I don't see any other visual defects / failures, even with a magnifying glass. I plan to test some of the other components tomorrow. If I can find my other camera, I'll take some pics and post them.

    Gary
     
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