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Black and Decker 20V DC Lithium Sweeper Circuit Board Repair - Help.

Discussion in 'Sensors and Actuators' started by cajoromi, Jul 26, 2019.

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  1. cajoromi


    Jul 26, 2019
    IMG_20190726_113815 burnt.jpg IMG_20190726_113956 burnt.jpg Hi,

    my leaf blower stopped working and upon taking it apart I discovered burn marks on the circuit board. The marks were around what appears to be two solder dots as outlined in the photo's I've attached.

    Can anybody please help to identify this specific part and tell me, if possible, how to repair it? My electrical knowledge is limited but I'll do my best to assist with any inquiries.

    Sorry in advance for the quality of the pictures.

    Any instructions or suggestions would be greatly appreciated.
  2. dave9


    Mar 5, 2017
    You need a new camera far more than a leaf blower. :p

    It's probably (was) a diode, with the anode end of it on the right solder pad as pictured, or an inductor, but I could easily be wrong. Is there a letter and number next to that spot, like D3, or L2, et cetera?

    A better focused, top-down (at 90') high resolution picture, and telling us where the black wire to the left of the solder pads goes (direct to the battery negative?), might help.

    How old is it, how long was it running at time of failure? It looks REALLY clean inside for a blower so I'm guessing either you cleaned it or it hasn't been used much at all.

    The bigger issue in my mind is was this a defective component, a design flaw, or some other fault. If one of the latter two possibilities, merely putting a replacement (of exact same) component in may just blow again.
    Last edited: Jul 26, 2019
  3. cajoromi


    Jul 26, 2019

    Thanks for your reply. I posted this question on another forum and this seems to be the winning answer:

    That looks like there was a resistor there; look around inside the casing for a part about that size.

    Looking at how it's wired, that a PWM driver section for the motor; the driver is the 8 pin chip, and the lower part would be a diode, near the red wire there.

    That would likely be a current limit resistor/fuse, and it looks like it did its job, lol.

    I would guess it would be a small value resistor, like 0.1 ohms or smaller.

    I'd try a single strand of wire from a piece of multistranded appliance cord; one "thread" out of an 18awg zip cord cable is about 40awg, and that blows at about 20A.

    If you can find the original part, there may be a number on it, but I doubt it.

    Make sure the motor spins easily before you do this; the motor stalling is what cause this, either there was crap in there, or the bearings in the motor are bad.

    Try it before you put it together, it's easier to put out if it catches on fire. [​IMG]
  4. dave9


    Mar 5, 2017
    I doubt they'd put a resistor (above 0 ohms) in series with the load. If it was a resistor, I'd get a 0 ohm of the right footprint, not take strands out of a piece of wire to guesstimate the gauge and current. Besides the wire would be unlikely to blow like a fuse, would instead melt the solder and fall off.

    Were you operating it when it failed? Did you notice something that might cause the motor to stall? Some cordless power tools can be (easily) stalled because of the nature of the work and motion produced, but a sweeper is a different setup in that it's only moving air, very little change in load unless it has a mulch feature and you were currently mulching with it, which seems very unlikely considering how clean it is inside and the general lack of power a 20V cordless blower has (unsuited for mulching).

    As I wrote previously, it looks very clean inside like it has not ran long so it would be unusual for a motor failure, but certainly you should check to see if the motor spins freely, and if the wires have connectors (instead of crimp or solder) you could disconnect them and give the motor an alternate DC power source (wire jumpers direct to the battery would work) to see if it is operating properly.

    I'm still not expecting this to be as simple as a motor failure or just replacing the (if it is a) 0 ohm resistor-as-fuse to fix it permanently, but a defective component, bad solder joint, are possible.
    Last edited: Jul 26, 2019
  5. Martaine2005


    May 12, 2015
    Without a clearer photo and no response from the op, who knows..
    Possibly even unpopulated pads. Probably not though due to burn marks.
    You have been asked several questions, please answer them.

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