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Resistor Value

Discussion in 'Datasheets, Manuals and Component Identification' started by H2814D, Oct 27, 2018.

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  1. H2814D

    H2814D

    78
    9
    Nov 4, 2017
    OK guys. This is embarrassing, but I cannot identify the value of this resistor from the color bands. Know that before coming here (as a last resort because this should have been simple), I have tried the color charts and the internet and the phone apps, but I just can't find this one. It appears the colors are: red, orange, silver, gold, and white. The color charts do not have silver as a selection for the third band, gold is not a selection for the second band, and white is not a selection for the fifth band, so my order should be correct. So it is two-three something.

    And thanks for the reply. I'm sure I'm about to get educated here shortly. :)
    IMG_6001.JPG
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,418
    2,788
    Jan 21, 2010
    That is an inductor.

    Look up the colour charts for inductor bands.

    I can't do that for you right now, but I'm sure that's the hint you need, and someone else will probably tell you the same thing (and have time to look it up for you) if you wait a short while.
     
  3. H2814D

    H2814D

    78
    9
    Nov 4, 2017
    I actually appreciate you not having done it, so I could do it myself. I did not know it was an inductor, so now it makes sense. Now if my reading of the chart is correct, it is a .23uH inductor. Thank you *steve*. Wait. Now using another chart gives me a value of 2.3uH. So now I'm confused. Is the last white band insignificant?
     
    Last edited: Oct 27, 2018
  4. Ylli

    Ylli

    339
    94
    Jun 19, 2018
    I think it still could be a resistor. What is the designation on the PCB where you removed it? Does it say Rxxx or Lxxx?
     
  5. H2814D

    H2814D

    78
    9
    Nov 4, 2017
    It actually does say Rxxx. That was why I thought it was a resistor as well. But then the color codes from the chart do not compute.
     
  6. kellys_eye

    kellys_eye

    4,275
    1,146
    Jun 25, 2010
    'Context' will be the key here. Where in the circuit does this part 'fit'? Can we see a picture of the board where it was removed from?

    Inductors (assuming it is one - and I agree with (*steve*) on this) like that would either be part of a resonant/filter circuit or simply decoupling in a power line.
     
  7. dave9

    dave9

    958
    250
    Mar 5, 2017
    It looks intact to me, like it should give you a valid resistance measurement if it's a resistor so you don't need the color bands. However that wavy shape to the body of it, does look like it may be a wire wound inductor. Similarly, it looks intact to me so are you assuming it's bad and trying to replace it?
     
  8. H2814D

    H2814D

    78
    9
    Nov 4, 2017
    OK...working on getting the photo, but one end of this is connected to the (-) pin of the bridge rectifier and the other end is, among other things, connected to the (-) side of a large filter capacitor and the source pin (#3) of a power MOSFET (13NM60N). This is a SMPS. Does that help?

    While testing it in one direction with the voltmeter leads, it is reading between .2-.3 Ohms (my meter does not go past tenths), but usually settles at .2 and sometimes down to .1. Changing the leads initially gives me all kinds of various numbers and then it usually settles back down to the same .2-.1 Ohms. After reading about inductors, they usually ("ideally") should be at 0 Ohms, so this is close, but obviously wire will have some resistance. If it is a resistor, which I am now inclined to say it is not, it is reading about what it should (.23 Ohms) based on "some" of the color bands.

    Based on comments above, a failed inductor should provide a visual clue. Is that correct? There are no signs of this. Additionally, since an inductor is basically a coil of wire, it should conduct a current through it. This one does that.

    One last question. Do inductors have to be placed in the circuit a certain way (like a capacitor) or does that matter? My thoughts are no, otherwise there would be a marking on the board and the inductor would have a negative and positive side.

    Thanks for your replies.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,418
    2,788
    Jan 21, 2010
    Last question first. If an inductor has only 2 leads (and no magnets) then it can be connected in circuit either way around.

    If this was an inductor, with 5 bands, typically you have a double-width silver on one end. Having a closer look now, and comparing it to the inductor colour charts, I will rescind my initial statement that it is an inductor. Green is a fairly common body colour for inductors and a relatively rare one for resistors (other than for vitreous enamel coated ones)

    However, the white band on the end has me somewhat puzzled. Reading it as a resistor it is either a 0.23Ω 5% resistor with an unknown white band or something which makes no sense whatsoever.

    However, a small inductor is unlikely to be found placed between a rectifier and a filter capacitor. A low value resistor might be placed there to limit switch-on surge current.

    I have also been assuming this is a small device, around 1cm in length. I now imagine it is somewhat larger.
     
  10. kellys_eye

    kellys_eye

    4,275
    1,146
    Jun 25, 2010
    The last band may be temperature coefficient although 'white' isn't such a colour - maybe the resistor is/has suffered some heat stress and changed from something else?
     
  11. H2814D

    H2814D

    78
    9
    Nov 4, 2017
    The component (mystery as it is) is the same size as a typical 1 or 2 watt resistor. See attached pics.

    I just tried to find a .23 Ohm (230 mOhm) resistor and had zero luck finding that value anywhere. I also tried to find a .23 uH inductor and had the same luck. I am just going to have to assume and hope this item is good, based on the visual characteristics and the component testing I've already done with it. There is no schematic available either.

    I don't believe the color bands are other than stated. There is zero indication of heat damage on it anywhere.

    Since an inductor would have a magnetic field around it when current is passing through it, I could try that and see if the component becomes magnetic, but would a resistor become magnetic as well? If I did try that, how much of a current should I try without smoking it? I hesitate with this, because I am unable to find a replacement anywhere.

    Thanks for the help so far.
    IMG_6009.JPG IMG_6011.JPG
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,418
    2,788
    Jan 21, 2010
    You're going to have fun finding anything with "23" because in the standard series that use 2 digits and a multiplier, 23 is not a standard value

    Even in the E192 you only get 229 or 232.

    That doesn't mean these values aren't made, they're just not standard.

    However, given that it still shows continuity, the chance that there's something wing with it is actually rather small.
     
  13. Ylli

    Ylli

    339
    94
    Jun 19, 2018
    Outside of my expertise, but isn't the last band sometimes used to indicate 'reliablilty' or 'failure rate'?
     
  14. dave9

    dave9

    958
    250
    Mar 5, 2017
    Maybe we need to back up a bit. Why did you remove it?

    I assume the PSU has failed? Did you probe it with a meter, measure voltage coming from the bridge rectifier and find none after this component, OR it blows the fuse immediately when turned on? If so the fuse blowing is "most likely" a shorted transistor, but it would be better to look at the PSU as a whole first, rather than focus on only one component again.
     
  15. H2814D

    H2814D

    78
    9
    Nov 4, 2017
    I removed it because I found two other low Ohm resistors on the board that were bad. This one was wedged in between a couple of coils and I couldn't test it while it was still on the board by removing one leg. My probes wouldn't get in there without contacting other stuff. The fuse is fine as are all of the transistors. I simply needed to know what it was, because I couldn't identify it with the color bands. Because the board has it marked as a resistor (R803), I will use that and conclude it is ok, but my original question about the odd color bands remains. :) R803.JPG
     
  16. kellys_eye

    kellys_eye

    4,275
    1,146
    Jun 25, 2010
    Any chance of finding the schematic?
     
  17. Robert_fay

    Robert_fay

    124
    34
    Jun 15, 2017
    I actually wrote a post about these, however I was not able to find any with a white 5th band. Here would be one that has a black 5th band. There is also often a more noticeable gap between the 3rd and 4th band.
    [​IMG]

    https://forum.digikey.com/t/when-your-5-band-resistor-is-not-a-5-band-resistor/1501
     
  18. H2814D

    H2814D

    78
    9
    Nov 4, 2017
    I have tried to find a schematic, but no luck on that. It would make things so much easier.
     
  19. kellys_eye

    kellys_eye

    4,275
    1,146
    Jun 25, 2010
    Can we see a picture of the WHOLE board? Top and bottom.
     
  20. H2814D

    H2814D

    78
    9
    Nov 4, 2017
    Wish I had seen this earlier. The PS is back in service. Two low ohm resistors (but not the one responsible for the post) and a diode were replaced and brought the unit back to life.
     
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