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  1. #1
    Enlightened Preamp's Avatar
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    Red face Repairing a Fenix LD-01, need some help

    Hello everybody.

    This is my first post on this forum. I've found quite some good informations in here, so I thought I'll just sign up and ask you pro's for some help...

    I am trying to fix my three years old Fenix LD-01 for the second time now . The error is basically the same, the solution, obviously, is not. But let's start from the beginning:
    When the Fenix stopped working for the first time, I could only get some light out of it twisting and pushing/bending it quite hard. My first thought was that the lower case didn't make a good contact to the PCB, so I added some solder to add up some height to the contact.
    Unfortunately this made things only worse, because the irregular surface added lots of switch bounce, driving the mode selector mad .
    So I went on and completely disassembled the Head. I cleaned the electronics from epoxy, took the PCB stack apart, and resoldered each and every component. After putting everything back together, it actually worked fine again. Up till now, about three weeks long.

    The actual problem now is this: When I turn the LD-01 on, it eventually starts to flicker uncontrolled for a couple of seconds. During this flicker, it manages to cycle through the modes until it ends in high power mode, where it continues to work as expected. Turning it off and on again, restarts the flickering process until it ends in high power mode again.

    So here I am now, ripped the whole thing apart again and wired it up do so some testing. The solder joints all seem to be OK now, I can't produce any misbehavior through knocking or pushing anywhere on any of the parts. I noticed that the core of the coil is broken, though. So I replaced it with another coil I had lying around, for testing purposes. This stopped the inductor whine (since I used a coated one ), but nothing else changed. Tried the same with the capacitors, but to no extend.

    A bit frustrated and not knowing what to do anymore, I started drawing a schematic, as good as possible. While measuring the connections, I tried to check for bad vias, but everything seems fine to me.
    Maybe some of you guys recognises which kind of driver is used and/or has some tips for me what else to look for.


    Thanks in advance and kind regards,
    Lasse





  2. #2
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    Default Re: Repairing a Fenix LD-01, need some help

    Not saying that this is the case, but have you checked the tailcap electrical contact ring? It has two indents in it too allow for tightening, and loosening. Many Fenix's have had the issue of the contact ring unscrewing a little and causing finicky contact with the end of the flashlight body.

    Bill

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    Administrator Kestrel's Avatar
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    Default Re: Repairing a Fenix LD-01, need some help

    Wow, nice first post. Good luck on the repair,

  4. #4
    Enlightened Preamp's Avatar
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    Default Re: Repairing a Fenix LD-01, need some help

    No, I did not check it. But since I have the electronics laid out on my bench, soldered wires to the battery contacts and connected them to a power supply, I can exclude it for now, I guess.

  5. #5

    Default Re: Repairing a Fenix LD-01, need some help

    Quote Originally Posted by Bullzeyebill View Post
    Not saying that this is the case, but have you checked the tailcap electrical contact ring? It has two indents in it too allow for tightening, and loosening. Many Fenix's have had the issue of the contact ring unscrewing a little and causing finicky contact with the end of the flashlight body.

    Bill
    Are you thinking of the LD10, rather than the LD-01? The "tailcap" on the LD-01 is essentially the body of the light, and is over an inch long - I can't see any contact ring with indents like on a bigger light down there, just the spring.
    Sorry I can't help OP.

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    Default Re: Repairing a Fenix LD-01, need some help

    Quote Originally Posted by Preamp View Post


    I cannot tell you what the fault is, but I can give your a good idea about how it works (Maybe you have already figured that out):

    The PCB with the inductor is a boost converter that increases the voltage up to led level, i.e. 3.5 to 4 volt.
    On the other board you have a voltage detector (marked 22), a microprocessor (unmarked chip) and a transistor (marked AGSE).
    C3 and C4 is used to maintain power to the microprocessor when you turn off/on to change brightness level, this fast power drop is detected by "22" and signalled to the microprocessor.

    You can check that the boost converter has a stable output voltage.
    The wire from "22" to microprocessor must have a stable voltage, until the voltage drops, then it must change to another voltage.
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    Default Re: Repairing a Fenix LD-01, need some help

    HKJ,

    thanks for explaining the circuit. I was quite sure about the boost converter and the FET, the microcontroller was a careful guess, but I had no idea about the voltage detector.
    The wire you mentioned is stable at 0V when the circuit is running in high power mode. In the 'flicker mode' this one is also flickering .

    If I am assuming correct, I could simply leave the first board out and connect the second one directly to 4V, right? I'll try this tomorrow.

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    Default Re: Repairing a Fenix LD-01, need some help

    Quote Originally Posted by Preamp View Post
    If I am assuming correct, I could simply leave the first board out and connect the second one directly to 4V, right? I'll try this tomorrow.
    I will recommend including a resistor in series with the power supply, maybe 1 ohm. This way you avoid driving the led into a very high current direct drive mode.
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    Default Re: Repairing a Fenix LD-01, need some help

    My bench supply is current limited. The whole circuit uses about 800mA in high power mode, so I'll start out with something like 500mA.

    Do you have an idea which type of boost converter might be used here?

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    Default Re: Repairing a Fenix LD-01, need some help

    Quote Originally Posted by Preamp View Post
    My bench supply is current limited. The whole circuit uses about 800mA in high power mode, so I'll start out with something like 500mA.
    500mA is a bit high, remember that the boost converter will nearly triple the voltage, i.e. you only have about 270mA for the led and processor.
    Many bench power supplies is a bit slow in current limiting, i.e. you might get a current spike, it is much safer to include a resistor in the circuit.


    Quote Originally Posted by Preamp View Post
    Do you have an idea which type of boost converter might be used here?
    I do not know what chip is used.

    My explanation was based on your schematic, not on studying the internals of a LD01.
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  11. #11
    Flashaholic* koala's Avatar
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    Default Re: Repairing a Fenix LD-01, need some help

    Chinese chips hard to find? You are probably looking at the wrong place. Plenty if you know where to start

    http://www.utsource.net/aic1610.html


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  12. #12
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    Default Re: Repairing a Fenix LD-01, need some help

    koala, I only looked at some local suppliers. For a valid reason, as it seems: Utsource has a minimum order of 10 bucks plus 25 shipping to germany! That's too much for not being sure if it's not the PCB.
    Looks promising though, I'll keep it in mind for future reference.

    I'm currently working on an LED-based bike light where I need a PCB for, too. This small board here will fit in an empty corner easily, so the board costs are almost nil. Ordered the LTC3490 as sample, so it's free, too. My employer is going to place an order at RS-Components soon, so I'll save shipping costs and get inductor and capacitor from there. Not exactly my favorite components and I'll have to get 5 pieces at once, but still cheaper than Farnell's shipping.
    Turns out not to be as costly as expected in the first place .

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