Grinding away a resistor?

Discussion in 'General Electronics Chat' started by retched, Feb 20, 2010.

  1. retched

    Thread Starter AAC Fanatic!

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    What would be the reason for this:
    [ed]
    updated photo for clairity
    [​IMG]
    [/ed]

    It is the best shot I could get, sorry about the blur..why would you grind away a resistor? is it because the manufacture bought the wrong resistors and edited these to make them work?

    It looks bad in the photo, but it is "perfectly" ground. Not "blown". no traces of heat or damage other than intentional.
     
    Last edited: Feb 21, 2010
  2. Wendy

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    I've never seen anything like it. What country made it? China?
     
  3. retched

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    Hong Kong-China. The product is a Dial-A-Temp from KB ELECTRONICS, INC.
    Coral Springs, FL
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    That looks like a way to make a high resistance out of a low value resistor. And you actually can cut a notch into a 2 watt carbon resistor to produce a higher resistance. As the notch gets deeper, the resistance goes up while the conductive path gets smaller.

    That says that employee time is worth less than carbon resistors, though.
     
  5. retched

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    That was my thought. We have 100 ohm resistors, we need 500 ohm... here Jimmy, grab a file and a meter and make these into 500 ohm resistors. I'll give you a glass of water and a dollar a week.
     
  6. retched

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    I think i could understand it more for high accuracy test equiptment. But, without any protection from burning a house down? This is straight from the mains. about a half millimeter from the wiper on the POT.
     
  7. hgmjr

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    Jan 28, 2005
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    If this has to be done then there is one precaution I believe should be exercised. Once you open up these gapping wounds in the resistor, I would expect that some provision would need to be made to reinstate the breached protection against the absorbsion of moisture with its inevitable impact on the components resistance. Perhaps something like clear enamel paint would need to be applied to the resistor to re-seal it.

    hgmjr
     
  8. beenthere

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    That's a job for corona dope.
     
  9. davebee

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    Oct 22, 2008
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    A friend's car once had a piston pin retainer break, and the piston pin worked its way sideways until it started to rub on the cylinder wall, and proceeded to mill a beautifully neat, clean slot into the cylinder wall. It was so neatly done that my friend thought at first that it was meant to be there for some reason, porting gasses or something.

    My point is that maybe a mechanical accident could have cause this? Could a rotating shaft have rubbed on the resister? It sounds not very likely but you never know...

    Speaking of slotted capacitors, I've seen ceramic caps with neatly cut slots where the slots contain built-in spark gaps for overvoltage protection (this was from an old television set high-voltage circuit). Maybe that was the purpose of the Fluke caps?
     
  10. spinnaker

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    And I will give you a $100 if you can find someone working in a Chinese factory with the name of "Jimmy". :)


    BTW Does your camera have a macro setting? Also helps if you but more light on the subject.
     
  11. retched

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    I am actually a pretty proficient photographer.. Worked for a few years selling cameras and teaching photography. But this was a cell phone camera. No such options.

    I will use my camera and repost for interest.
    [ed]
    [​IMG]
    [/ed]
     
    Last edited: Feb 21, 2010
  12. spinnaker

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    Now that is a photo!


    Yeah those cell phone cameras stink. :)

    Loots like they ground the PCB too. Probably had a bunch of boards built up then they realized there was a design problem or a board stiffing problem. Must have been easier for "Jimmy" to grind them away then replace them.
     
  13. retched

    Thread Starter AAC Fanatic!

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    Poor, poor Jimmy. I can see the guy (or girl) sitting at a scope with a huge box of these things on the left, a dremel in their hand and a box for the "fixed" ones on the right. On the wall there is a sign that says: "You live for the good of the Company"
     
  14. PackratKing

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    Jul 13, 2008
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    All Hail Corona Dope !!!!!!

    Marvelous stuff ! Is there a current source ? or a useable equal ? ...--... running desperately short.
     
  15. retched

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  16. KMoffett

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    "here Jimmy, grab a file and a meter and make these into 500 ohm resistors."
    Definitely cheaper and takes up less space than a trim pot. ;)

    ken
     
  17. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    By grinding the resistor its value must be gone up as the carbon bar (the black part) is getting thinner.
    A bit stange method.

    Greetings,
    Bertus
     
  18. Wendy

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    Mar 24, 2008
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    But effective, if only for the short term. Notice the type of resistor? Those old suckers drifted badly before they were modified, though modified doesn't seem strong enough. With the seal broken and the material exposed to air I suspect they walk all over the place, mostly increasing in value over time.

    I'm not sure of this, but it would seem the wattage would also decrease.
     
  19. retched

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    Dang, then this sucker should be worth fifty bucks!:eek:

    ;) -- kidding --

    there seems to be a good amount of interest in this resistor.

    Shall I pull it so I can read the value stripes then meter it to see what they got?

    I suppose I could O'scope it over a range and see how she holds.

    If no one cares, ill skip it.
     
  20. Wendy

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    I think the amount of interest is proportional to the amount of disbelief someone would do this. Kind of a techie nerds version of
    "Believe it or Not!".
     
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