Resistors

Discussion in 'Architecture & Engineering' started by John99, Nov 24, 2008.

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  1. John99 Banned Banned

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    I am trying to repair a PCB and need to solder a 2.2K resistor (see pic).

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    Does this need to go in a specific direction or will it do the job no matter which direction it is facing?
     
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  3. John99 Banned Banned

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    Any tips or links to electronic sites is also welcome.
     
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  5. John99 Banned Banned

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    i just fried my laptop.
     
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  7. leopold Valued Senior Member

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    17,455
    either way.
    tip:
    hold the resistor as close to the body as possible with needle nosed pliers to prevent the heat from damaging it.
    after soldering, snip off the excess leads with diagonal cutters.

    you can replace the old with the new one by crushing the body of the old one with pliers and then wrapping the leads of the new one around the pigtails of the old one.
     
  8. John99 Banned Banned

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    thanks. i just wanted to be sure but i made mistake by disconnecting the leads from a power supply and i did major damage. worst is a fried laptop. i am terrible with electronics. nothing ever works.
     
  9. cato less hate, more science Registered Senior Member

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    that sucks. well, it's the perfect time of year to buy a new laptop
     
  10. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    Let's see if I can remember my electronics school training...

    Black, brown, red, orange, yellow, green, blue, violet, grey, white...

    "Bad Boys Ravish Only Young Girls But Violet Gives Willingly"

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  11. leopold Valued Senior Member

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    17,455
    and to add to that:
    the first two bands are the significant figures while the third band is the multiplier.
    the fourth band is the tolerance.
    if the first band is double wide then it's a wire wound resistor.
     
  12. thecollage Registered Senior Member

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    what is inside of the resistor?
     
  13. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    7,028
    Magic!

    I think they are made of some sort of silicon. They sure smell nice when they fry.

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  14. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    Didn't know that part about the double wide part...I love learning stuff.

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    So in the resistor pictured, it has 3 red bands..Let's figure its value:

    Red=2

    So we have 2 as the first digit and 2 as the 2nd digit..with 2 zeros after...2200...so it's a 2.2kohm resistor! with a 5% tolerance. Fun fun...

    Let's try another:

    What would be a Brown, Black, Blue, Gold ?
     
    Last edited: Nov 26, 2008
  15. phlogistician Banned Banned

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    I used to have a little chart I got free from Tandy (Radio Shack to our US cousins) back in the day, although after a short while, I started to remember the values.

    In reply to MacG, 10MΩ, +/- 5%.

    Hey, I found a cool chart like the one I used to have!

    http://www.pc-control.co.uk/resistor_code.htm
     
  16. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    This is one reason you will never find a colorblind electronic technician

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  17. John99 Banned Banned

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    this looks like fun:
    http://www.pc-control.co.uk/computrain.htm

    i may try to fix the amp by changing the wires from the power switch to the pc board. i soldered thje resistor onto the back of the board but i dont think that was the problem. i did use a resistor with the same color coed: 3 red bands so i think i used the right one and i did smell something for a brief period after i flipped the ON switch but that could have been my imagination.

    how do you know if a resistor is working or not?
     
  18. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    Use a voltmeter to read the voltage across the resistor. Failed resistors usually open up...instead of shorting.

    If it's not black..and is connected to the circuit..it's probably working.
     
  19. John99 Banned Banned

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    I will take it apart again later to see what happened. When i use the voltmeter do i plug the amp into the wall?

    This is a guitar amp and everywhere i read that messing around in there without bleeding the caps can be fatal so i would rather have it unplugged the whole time i am working in there.

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    i have a volt meter with red and black lead but there is a dial on it with numbers, any thoughts on what number to use?

    To give you an idea:

    ACV -
    200V
    500V

    DCV-

    DCA-

    ah, i see now it has a selector for OHM. Guess that is the one to choose. My resistor is 2.2K.
     
  20. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    7,028
    Normally, you would take the voltage reading with the circuit hot...but with the voltages involved..I wouldn't chance it. Pull the resistor and check it with an ohm meter.
     
  21. John99 Banned Banned

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    a resistor alone will show up on the meter even if it is just sitting there?
     
  22. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    On the ohm meter setting it will...the meter puts out a small voltage of its own so it can read the resistance. That setting only works on a non-hot system.
     
  23. leopold Valued Senior Member

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    17,455
    resistors with a gold or silver tolerance band are precision resistors.
    not really sure of the value though.

    what is the tolerance if the 4th band is missing?
     
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