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Mad resistor bands.??

Discussion in 'General Electronics Discussion' started by 7Mark7, Jan 25, 2013.

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  1. 7Mark7

    7Mark7

    6
    0
    Jan 25, 2013
    Hi all,
    I'm new here and hoping some kind soul can help.

    It seems it simply can't be googled. :confused:

    I need to identify a failed resistor,

    The bands are:............. Brown, Black, Silver, Brown , Black.
    Or from the other way Black, Brown, Silver, Black, Brown.

    It's from a power supply board. Before I can order the other dead parts (transistors) I need to know the value of this one.

    Any help will be much appreciated.
     
  2. shrtrnd

    shrtrnd

    3,814
    516
    Jan 15, 2010
    Typically, Silver is the .01 multiplier for tolerance.
    You'd need a really good ohmeter to read that.
    Let me ask, how did the resistor fail? Are you SURE it's a resistor?
    Resistors that overheat often cause the painted color bands to change color.
    You might be looking at an inductor, ... or even a capacitor anymore.
    Does the PCB it came from have a silkscreen designator for the part?
    ('R' for resistor, 'L' for inductor, 'C' for Capacitor)
    Is it in a molded case? Anything in particular you can tell us about it's physical construction?
     
  3. 7Mark7

    7Mark7

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    0
    Jan 25, 2013
    Thanks for the reply shrtrnd.

    It's mad I know. Deffo a resistor, even marked on the board as 'R' .

    From what I can make out it blew a small hole in it, probably at the same time as/or resulting from the failed Mosfets. I think it's some kind of fused resistor. I'm lost as to the bands though.
     
  4. 7Mark7

    7Mark7

    6
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    Jan 25, 2013
    Sorry, A little bit of background.

    The PSB has the usual transformers, inductors, caps, diodes, an NTC.......

    Nothing too strange to me (although i'm no expert at all).

    It's from my TV at home.

    The little board mounted T5 fuse was open circuit, two Mosfets were short circuit.

    This resistor is open circuit on every level of my meter, as it probably would be with small hole in the side.

    Never come across these bands though.:confused::confused:
     
    Last edited: Jan 25, 2013
  5. Raven Luni

    Raven Luni

    798
    8
    Oct 15, 2011
    Are you sure its silver? Not grey or white? Resistors use all 3 of these colours so it is only silver if it is actually shiny. Gold and silver are typically only used for multipliers and tolerance and would only appear in bands 4 or 5 of a 5 band code, never anywhere else.

    Having said that - even if it was grey or white it is still questionable. Band 5 is the tolerance band which cannot be black - so it must be the other direction (brown = 1%). I've never seen a number value starting with a 0 but its not exactly illegal. Assuming your 'silver' is grey this would be an 18 ohm resistor but the usual way to band this would be brown, grey, black, gold (and brown for your 1% tolerance)
     
  6. geekygenius

    geekygenius

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    Jan 21, 2013
    Could you measure it with a multimeter?
     
  7. 7Mark7

    7Mark7

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    Jan 25, 2013
    Hi Raven,

    I completely understand what you are saying, and appreciate the reply.

    I've just taken a picture with my phone and lit it up with a torch to help see the colours.

    If someone can tell me how to get it from my phone to here, I'll post the pic.

    Thanks.
     
  8. 7Mark7

    7Mark7

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    Jan 25, 2013
    Hi Geeky.

    Open circuit every level.
     
  9. Raven Luni

    Raven Luni

    798
    8
    Oct 15, 2011
    Can you plug your phone into a USB port on your computer? If so it should hopefully show up an an external drive and you can upload the file using the options in this forum
     
  10. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    As shrtrnd already said, silver in the 3rd band is a multiplier of 0.01, which means brown black silver is a 0.1 Ohm resistor, which will probably read as 0 on your multimeter even if it is not shorted.

    Bob
     
  11. 7Mark7

    7Mark7

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    Jan 25, 2013
    https://www.electronicspoint.com/attachment.php?attachmentid=7064&stc=1&d=1359151587

    Sorry guys.

    Took me ages.
    Now its the wrong size.:confused:

    No hang on ....it works if you click the thumbnail.

    As you'll see the black band on the left is hard to see from the pic. Both browns are deffo the same shade in real life, and the centre band is what I would call Silver.
    The hole in it is on the other side.

    Has anyone seen anything like it.?????
     

    Attached Files:

    Last edited: Jan 25, 2013
  12. geekygenius

    geekygenius

    27
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    Jan 21, 2013
    ?

    If I was just a total noob, its because I am.
     
  13. gorgon

    gorgon

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    24
    Jun 6, 2011
    The problem with this picture is that there should not be a black at the end or a silver in the middle.

    Silver is a /100 value, but in the wrong position for a 5 ring component. If you discard the last black ring the value is 0.1 ohm 1%.
    Black is not a valid tolerance ring(last) or first digit. Silver is not a valid 3rd digit in a 5 ring code.

    Everything is a bit confusing, even for one that has been in the trade for almost 40 years.

    How old is this unit?
     
  14. Raven Luni

    Raven Luni

    798
    8
    Oct 15, 2011
    Went back and read the fist post again.

    If its failed then trying to measure it is useless.
    You say a hole was blown in it. I've never known that to happen to a resistor - they tend to blister and burn. The only things I've manage to blow holes in are semiconductor devices like transistors and diodes.

    Can you take a picture of the hole?
     
  15. davenn

    davenn Moderator

    13,808
    1,943
    Sep 5, 2009
    Ohhhh I have seen a few resistors over the years that have had a hole blown in them
    It would commonly be the ones that had a spiral of carbon/metal film and they would just pop like a fuse somewhere along the spiral and leave a small hole in the enamel coating

    Dave
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,489
    2,830
    Jan 21, 2010
    My thought is that it might be an inductor, and the failure might well match what has been explained (but not yet seen).

    Very unusual to see bands so close to both ends...
     
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