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Need Help Repairing Bicycle LED Lights

Discussion in 'Troubleshooting and Repair' started by JohnS0N, Nov 14, 2016.

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  1. JohnS0N


    Nov 14, 2016

    a noob here. In the forums as well as in electronics. I do know how to solder a bit, measure volts and connect + with +, other than that please do not assume much knowledge.

    I would like to repair these LED lights here and for the purpose, I made a few videos and pictures.

    Please watch the below video and listen to my explanation with perfect pitch English accent.

    In this second video, I demonstrate how you need to find that "sweet spot" in order for the light to shine bright like a...

    Now my question is how do I fix this? How can I make this small piece to shine when I press it in the middle (so it can actually work with the silicone body on), and also that it will work when pressed lightly (else it may also not work when it is covered with the silicone body). As seen in the above video, the light just works when pressed somewhere on the far left and you need to press it quite a lot.

    Here we also have some pictures. These first two are of a working circuit. One back and one front.



    These other two are of a circuit whose "little metal cap" I took off, so that you can see what is below the metal cap. By taking off the metal cap, I have of course also "destroyed" the pins on the other side. These were holding on to the cap and providing connection with the battery. Here also one back and one front.



    Now I have about 20 of these lights that I would really like to fix. I don't like throwing products and materials in the bin if there's a chance of fixing it! Thanks so much for reading this and for any kind of help in explaining how these lights actually work and how I can fix it.
  2. mikey5791


    Jun 7, 2013
    Hi Johnson,

    Can you use "Upload a File" tab to upload your pictures; showing both front and back side.
    I believe these bicycle lights are not faulty since you said you the light works when you pressed on lightly and you just want to change the switch on function.(maybe modify the switch function)
    Am I correct?
  3. JohnS0N


    Nov 14, 2016
    Of course, however to comply with the size regulations, I had to crop the pictures and make them smaller. So these below do not contain as much detail as those above.

    The first two pictures are of the complete circuit (it is complete, but does not work normally, as explained above you need to find that sweet spot).

    And two the last two pictures are of the broken circuit. I broke one just so you can see what is below.

    Attached Files:

  4. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    It is likely the contacts are corroded. Have you tried cleaning the contacts on the PCb as well as the little dome that closes the circuit between the outer ring on the pCB and the center contact on the PCB?

    The dome seems to have contact with the outer ring on the PCB by teh mechanical fixing only (bent tab on the bottom). You can try to improve this contact by soldering it to the PCB in the two locations indicated below:
    Make sure you solder with a hot iron and quickly. If you heat the dome for too long, it may lose its springiness and work no longer as expected.
    JohnS0N likes this.
  5. mikey5791


    Jun 7, 2013
    From your picture (small_incomplete1), I can see the outer track is for negative(-) DC polarity
    while the inside track (near the white circle) is for positive(+) DC polarity.

    But I wonder if you know the battery DC voltage needed for the LED light since it is not shown in your picture. Should be around 3 volt button cell type. Do you have the battery model no. to confirm this?
  6. JohnS0N


    Nov 14, 2016
    @Harald Kapp - Thank you so much for your reply, I will try to solder on those two points. It is correct that the dome has contact with the outer ring only by mechanical fixing.

    I did try cleaning it on your first two mentioned posts, but I do not understand what you mean with "center contact on the PCB"? If you are referring to the one below the dome, it is quite hard to take off the dome without breaking it. The two bent pins on the other side are very fragile.

    I will report back if the soldering had indeed fixed the issue.

    @mikey5791 - Indeed, the battery is 2x 3V. It is a CR2032 model.
    Last edited: Nov 15, 2016
  7. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Indeed, this one.

    Not all is lost, if you succceed in soldering the dome back as suggested above. You will then not need the pins any more.
  8. 73's de Edd

    73's de Edd

    Aug 21, 2015

    Sir JohnS0N . . . . .


    Here is the operation of your unit, all explained within the illustration:

    There is the Lithium cell at the left and the dotted yellow line indicates the reforming bend needed to be restored to get battery clamping contact again.
    Looking at the right photo we see the circuit foil paths, with the outer circular peripheral foil carrying battery contact to your two LED connections. also there is your tactile Klixon type keyboard contact.
    You need a good typewriter eraser cleaning of all of the YELLOW circled contact areas and a cleaning off all of the gold flashed foil on the PCB proper.
    The keyboard cap then has its RED alignment tabs inserted in the PCB holed and reinstalled.
    It was said . . . .
    Not all is lost, if you
    succeed in soldering the dome back as suggested above

    The corner triad tips have to slide outwards laterally, as the dome is pushed down.

    VERY FREQUENTLY they used a layer of clear tape over the whole top pad dome to keep out contaminants.
    (But it additionally holds down the dome)

    Considering that you have cleaned all potential dodgy contacts and connections . . .here is its manner of operation.
    The WHITE blob is encapsulation covering up an integrated circuit.
    Its commonly called a C.O.B. (Chip / Circuit on Board )
    There are 5 related connections being made into it.
    The RED main 3V at the botom.
    A BLACK ground connection comes in from the side
    A RED LED drive leaves at the very top, to the LED s.
    A PINK COB line activates the internal multi function menu cycle.
    When you activate the P.B. switch for the first time, +3V is fed thru the PINK line into the COB and activates a solid state switch that completes the dotted RED path and the LEDS light up.
    The next push of the switch initiates a timer that flashes the SS switch on and off.
    The next press of the button changes to yet another flash speed .
    The fourth press of the button opens up the SS switch and all is turned off.

    If you done a good clean up and reconditioning, and if its still not operating, the next thing to try, is to get a short jumper wire and connect to any of the button's metal area or that shared solder blob beside it.
    The other end of the wire goes to either of the central LED s + connections.
    If the LED s light up, woe is you, as your very-very unobtainable COB is bad.
    A potential fix then, would be to use a push on push off SPST switch or a slide switch, to hard wire in between my Red dotted lines marked outer connections.
    Then its On and Off will be OK . . .but it no longer will makee the flashee-flashee..



    Thassssit . . . . .

    73s de Edd
    Last edited: Nov 16, 2016
  9. JohnS0N


    Nov 14, 2016
    It's the end of the week and I can confirm that soldering the dome on the two locations mentioned by Harald Kapp did not work. I tried on 3 different lights. The issue remains the same, you still need to find that sweet spot. I have also tried soldering on other points of contact between the dome and the "moon shape", but sadly that did not improve it either.

    Moving on, 73's de Edd... thank you so much for taking such an enormous amount of your time to illustrate everything. The amount of help I got to this question is really overwhelming. I did not expect such a detailed response. Thanks to your answer I now can understand how this light functions and will try your suggestions, remove everything and clean it again and see if I can perhaps repair it. Maybe even because of this illustration that showed me how it works, I can figure out the issue myself if the above suggestions do not work. I will try a couple of different things.

    QUESTION: What is a "good typewriter eraser"? Can you give me a name and model or a link?

    Thank you everyone for replying, this is a great forum you have here with a lot of helpful people as it seems!
    Last edited: Nov 18, 2016
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