trying to repair my daughters night light

Discussion in 'Technical Repair' started by me217, Apr 23, 2016.

  1. me217

    Thread Starter New Member

    Apr 23, 2016
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    hey everyone first post here, still learning about circuit boards. I'm after a bit of help repairing my daughters night light. 3 of the 9 LEDS are flickering when its on.

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    the labelled LEDs 1-3 are the green ones which are flickering.

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    the one the screwdriver is pointing to is LED 1.
    the other LEDs are Red and Blue. they all work fine but the Green flickers or sometimes doesn't even work. the power comes to that board from another board which just has some caps and resistors on it. if needed i can put up a picture of it. but I'm almost certain that isn't at fault.
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    @me217
    Touch a soldering iron to the two solder pads of the Green LED and the 0 (zero) ohm resistor next to it. Then touch the soldering iron to the three pads of the transistor Q1 which controls the green LED.
     
  3. me217

    Thread Starter New Member

    Apr 23, 2016
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    are
    are you thinking there is a bad connection in the solder? i'll give it a shot as soon as the iron heats up.
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Yes. That is the first, fastest, easiest and cheapest thing you can try. Add a bit if solder if you have some.
     
  5. me217

    Thread Starter New Member

    Apr 23, 2016
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    just gave it a shot. no luck, i also forgot to mention that the numbers are the order from worst to best as far as flicker goes. number 1 flickers quite badly two not as much and 3 not much at all.

    EDIT: i was wondering if its a voltage drop. also they don't seem to flicker until they hit full brightness, as they fade on and off in sequence. i have heard that different coloured LEDs require more power then others. Would green require more then red and blue.
     
    Last edited: Apr 23, 2016
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The LEDs are still good if they are lit. There is a bad connection somewhere upstream. If the bad connection is under the black glob of black epoxy, then you may as well buy a new night lite.
     
  7. me217

    Thread Starter New Member

    Apr 23, 2016
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    yeah, its not locking good. the other board receives 6VAC which directly runs a motor and then is converted to DC for the LEDs. would the oven reflow trick be worth a shot?
     
  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Yes but watch it closely. No need for smoke alarms ringing at thus hour.
     
  9. SLK001

    Well-Known Member

    Nov 29, 2011
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    Not after the IC is "globbed" over with epoxy. The expansion of the epoxy can rip the bonds off their pads.

    Actually, a better high-resolution picture of the backside of the board (the "green" side) would help with the diagnosis.
     
  10. me217

    Thread Starter New Member

    Apr 23, 2016
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    well its "fixed" now. and i use that term very loosely. i rewired it so it just stays on solid blue. i got a feeling that the transistor right near the power input is faulty. after cooking it. as it flickers on and that's it. ah well. win some you lose some. thanks everyone for the advise
     
  11. takao21203

    Distinguished Member

    Apr 28, 2012
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    The efficiency isnt good.

    The advertised product most likely will pulse LEDs
    Even some USB output converters can be hacked. For more than 5v !
    Without the usb socket these are small.

    But they cant do 40v or 60v. Its about the limit what is safe, like the voltage used for the analog telephone system.

    For real illumination you need a larger solar cell and probably a lithium battery. These solar lights from shops are just dots, and the cheap ones will suffer from rusting after a short time. Theres a lot of trash in the shops..
     
  12. hp1729

    Well-Known Member

    Nov 23, 2015
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    The blue requires a higher voltage. Nothing special about the green. How is your confidence on buying and changing LEDs and transistors?
     
  13. me217

    Thread Starter New Member

    Apr 23, 2016
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    I would probably better off building a new board. Then trying to repair this one. I'd like to. I wonder if I could use some RGB LESs and have them go through the colours
     
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