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Rotary Tool Power Cord Resistors

Discussion in 'Troubleshooting and Repair' started by Terry Masri, Nov 15, 2017.

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  1. Terry Masri

    Terry Masri

    3
    0
    Nov 15, 2017
    Hi everyone! First time here. I have an Einhell (German brand) rotary tool that stopped working recently. After cracking the case open I discovered that the the hot wire in the power cord broke on the inside of the tool before the power switch button. Easy fix I thought until I discovered that both the neutral and hot wires are each connected to a black cylinder before being connected to the power switch. I'm an absolute layman when it comes to electronics, but I'm assuming that these black cylinders are in fact resistors even though they have no markings on them whatsoever typical of all the resistors I've previously seen. The cylinder is covered with a very thin and tough black skin akin to heat-shrink tubing. After managing to peel off some of the skin, I noticed that there is a very thin copper wire wrapped around a black cylinder, or carbon clay as I later discovered, confirming my suspicion that they are resistors of some sort. The hot wire somehow pulled out of the resistor and there's no way of soldering it back into the carbon clay cylinder. Now I've never seen such an arrangement in all the power tools I've repaired in the past, watching how-to YouTube videos and looking at hundreds of images on Google where the hot & neutral wires are usually connected directly to the power switch!

    My question is, since it's not possible to determine the kind of resistors these are (no marking or writings whatsoever) in order to purchase a replacement, can I bypass these transistors without jeopardizing the tool or creating a safety hazard for myself? If not, how can I determine the type of resistors being used so I may shop for replacements?

    Any help would be greatly appreciated! I have this big project I'm working on and my rotary tool is essential to the completion of the project. I'd hate to think that I have to wait a few days or maybe weeks until I find and order replacements before I can continue working on my project!

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    Attached Files:

  2. Minder

    Minder

    3,006
    640
    Apr 24, 2015
    Looks like one in each lead, they are wire wound chokes with what like a ferrite core.
    The tool should run without it (bypassed) , but you could probably repair that one or make up another using the same core, use heat shrink on it afterwards.
    M.
     
    Terry Masri likes this.
  3. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    I agree with Minder but you can confirm that it is not a resistor by comparing with the good one.

    The chokes are used to reduce noise sent into the mains from the commutator intermittent contact.
     
    Terry Masri likes this.
  4. Terry Masri

    Terry Masri

    3
    0
    Nov 15, 2017
    You guys are truly awesome! This goes to show that I really know nothing about electronics. Thanks for saving my project!
     
  5. Terry Masri

    Terry Masri

    3
    0
    Nov 15, 2017
    UPDATE: After close examination and further research online, I can confirm that they are in fact wire wound chokes and not resistors, and after connecting the mains directly to the power switch button (bypassing the chokes), it worked perfectly. I'm still not sure how removing the chokes affects the performance of the tool since I don't know what "reducing noise" actually means in electronic jargon, but I'm assuming the chokes don't play a critical role in the operation of the tool since nothing exploded in my face afterwards and I was able to work on my project for hours afterwards without any unpleasant surprises.

    Thank you guys again! YOu saved the day!
     
  6. Minder

    Minder

    3,006
    640
    Apr 24, 2015
    Not the operation of the tool, but general noise imposed on the AC line.
    Max.
     
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