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Is this a resistor? Help me identify please.

  1. Mar 18, 2010 #1
    I need some help identifying what I'm pretty sure is a resistor. I have a power supply that blew up, I opened it up and everything looks ok except for this.

    resistor-2.jpg
    resistor.jpg

    The color bands are:
    Brown
    Blue
    Silver
    Gold
    Black

    The only problem is that silver isn't a valid color for the third band. I know gray is, but it definitely looks silver to me. What else could it be?

    If I use gray for the third band I get a 16.8 ohm 20% resistor, what wattage do you suppose it could be using the penny for scale?

    Thanks for any help you can offer.
     
  2. jcsd
  3. Mar 18, 2010 #2
    Most likely .25W to .5W. I am pretty sure that it is not any higher than .5W.

    I am also pretty sure that it is a resistor.
     
  4. Mar 18, 2010 #3
    Try this:

    http://www.dannyg.com/examples/res2/resistor.htm

    This site gives 0.16 ohms +/- 5%. Is this a series or shunt resistor in the power supply? Is it part of a feedback loop? Perhaps knowing the function of the resistor will help determine its value.

    Bob S
     
  5. Mar 19, 2010 #4
    Your link is for a 4 band resistor, mine is a 5 band. And I still can't figure out why the third band is silver, which isn't a valid color.

    http://hirophysics.com/Labsheet/resis-codes/5-band.jpg [Broken]

    I'm not sure what the function is, the resistor wasn't very easy to get at, as there's a lot of stuff on top of there it was and I had to use a soldering gun on the back of the board and tweezers to pull it out. I figured if I could figure out what to replace it with I would just solder it to the back of the board and not have to do major disassembly.
     
    Last edited by a moderator: May 4, 2017
  6. Mar 19, 2010 #5
    Other than silver, you have to guess at the other colors. The paint oxidizes and changes color. They always look like black and brown after a good cooking.
     
  7. Mar 19, 2010 #6

    uart

    User Avatar
    Science Advisor

    Yes reading burnt resistor colors is always a pain_ITA.

    It looks like it doesn't follow the standard for a 5 band resistor. This leads me to believe that it may actually be using the 4 band scheme (with the final black band as an unknown function).

    This would make it a 0.16 ohms at 5% tolerance.

    Where abouts in the circuit was it located n00b? Was it in series with the output (typically a low valued resistor like this is used here as part of the current limit circuit btw), if so then 0.16 ohms is certainly feasible. What is the rated output current of the unit?
     
  8. Mar 19, 2010 #7
    My friend,

    first you need to accept the fact that the condition of any resistor upon burning would be ............ !!

    Hence, if you are guessing it to be a silver, you need to realize what it might be like before.


    Anyway, silver is a very much unusual colour as a third band. Perhaps you should consider reading it as grey !!

    Hope for best !
     
  9. Mar 19, 2010 #8

    uart

    User Avatar
    Science Advisor

    Unusual is very much a relative term. If for example this resistor is in series with the power supply output then silver (sub one ohm) would be a very common multiplier for a resistor in that particular application.

    BTW. Forgot to mention this before n00b, but if this is a dual type supply then you might well find that the resistor has a "mate" of the same type and value in the other channel.
     
  10. Mar 19, 2010 #9
    You're right! I didn't even think of that, I can just measure the other one.
     
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