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Thread: Flashlight Troubleshooting with Multimeter

  1. #1

    Default Flashlight Troubleshooting with Multimeter

    I have a 4Sevens Preon P2 that had alkaline batteries leak while in storage
    I did some tests with a multimeter and wanted some help interpreting my findings

    1. Switch - seems good. I cycled the switch on and off. The meter alternately read 0/OL and 1 ohm/beep for continuity as I cycled the switch

    2. Body - seems no good. The meter showed no continuity between the bare aluminum on the front and back of the flashlight. There is corrosion build up on the inside walls of the body

    3. Head - not sure. I put the leads on the center and outer ring of the circuit board. There is no continuity and measured 1.5 million ohms.

    My main uncertainty is whether or not the head is good.

    For comparison, my other two 4Sevens lights that are known good:
    The heads measure approximately 5 million ohms
    They are different models however (Quark 2xAA and Quark 2x123)

    Thank you
    Last edited by Former_Mag_User; 10-26-2020 at 02:34 PM. Reason: typo.

  2. #2
    Flashaholic Katherine Alicia's Avatar
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    Default Re: Flashlight Troubleshooting with Multimeter

    readings 1 and 3 seem pretty consistant, but reading 2 seems almost impossible, to be that bad it would be crumbling in your hands, try putting a pin/needle on each probe and try reading 2 again, just stick the pins into the "metal" really hard.

  3. #3

    Default Re: Flashlight Troubleshooting with Multimeter

    Thanks

    I'm going to try giving the body a good scrub with vinegar, then alcohol

    Maybe lightly sand the contact areas too

  4. #4

    Default Re: Flashlight Troubleshooting with Multimeter

    So after looking at the construction of the light more closely, it appears that the body is in fact 2 pieces: the main shaft and the tailcap end, mated by bare aluminum threads

    there is corrosion inside those threads which does not allow continuity between the tail end/switch and the rest of the light

    I can't undo the threaded portion. I believe it has threadlocker from the factory as these two body pieces sandwich the clip in place. Coupled with the corrosion they can't be undone easily. I'm going to see if I can undo these 2 pieces without damage

  5. #5
    Flashaholic Katherine Alicia's Avatar
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    Default Re: Flashlight Troubleshooting with Multimeter

    sadly potassium aluminate is quite a hard crystal, and you`ll have to break thousands of these micro crystals all at once if it`s gotten into the threads, it`s not impossible but it`s quite hard to do, heating may help fracture them a little though.
    dissolving a small amount of oil in petrol and then soaking the thread in that will get the oil in really deep after the fuel evaporates, it May help you undo it.
    an Ultrasonic cleaner will help loads if you have one?

  6. #6

    Default Re: Flashlight Troubleshooting with Multimeter

    No kidding! I used a heat gun and 2 large pliers; I couldn't get it undone.

    I'm going to get a replacement body and cross my fingers the LED head wasn't damaged by the batteries

  7. #7
    Flashaholic Katherine Alicia's Avatar
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    Default Re: Flashlight Troubleshooting with Multimeter

    you need an acetylene torch, it`s can`t be stuck if it`s a liquid!

    it should be possible to test the head with a battery and a peice of wire, just to make sure first before commiting to further outlay.

  8. #8

    Default Re: Flashlight Troubleshooting with Multimeter

    The LED lights up! The multiple output levels work as well

    Thank you for helping out

  9. #9

    Default Re: Flashlight Troubleshooting with Multimeter

    A can of Electrical contact cleaner from Walmart might help as well, just spray it down and let it dry on it's own which, while quick...will hopefully soak in enough to help loosen it a bit.

  10. #10

    Default Re: Flashlight Troubleshooting with Multimeter

    2 large channellock pliers broke it loose with some damage. There's so much corrosion through the body isn't worth saving

    I was able to salvage the clip though by breaking these two pieces loose

  11. #11
    Flashaholic Katherine Alicia's Avatar
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    Default Re: Flashlight Troubleshooting with Multimeter

    Glad to hear the business end is still working!

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