High Power Resistor?

Discussion in 'General Electronics Chat' started by AKnogood, Nov 20, 2014.

  1. AKnogood

    Thread Starter New Member

    Nov 21, 2013
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    I'm trying to fix a 5 years old dishwasher board that burned. One electrolytic capacitor dried out so I'm replacing all of them on the board (5) but there's also a resistor which I think is a high power resistor that I would need to replace. How can I know what value it was since it burned?

    [​IMG]
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Is it open? Put an Ohmmeter between the ends.

    I am guessing that it will be low Ohms, (<100). It looks to be a 1W power resistor.
     
  3. AKnogood

    Thread Starter New Member

    Nov 21, 2013
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    I removed the resistor from the board and the Ohmmeter shows 42K. Is it reliable even though the resistor burned?
     
  4. MikeML

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    Oct 2, 2009
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    Not likely. The first color band appears to be brown, so it would be either a 0.1xxΩ, 1.xxΩ, 1x.xΩ, or maybe 1xx.xΩ

    You will have to get a schematic from the maker, or trace out the power supply section.

    Begs the question, what caused it to overheat in the first place? The resistor is there to limit current; something elsewhere is drawing too much current; that smoked the resistor. You will have to also find the root cause;not just replace a resistor...
     
  5. AKnogood

    Thread Starter New Member

    Nov 21, 2013
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    I was able to find a picture of the electronic board. The resistor is located on the bottom right (R189). I think the bands are orange - brown - black (31ohm), what do you think?

    [​IMG]
     
  6. JDT

    Well-Known Member

    Feb 12, 2009
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    No! Note the slot in the board under R189 and V1. This is usually done when there is a high voltage between two tracks or that extra safety isolation is required.

    What I would do is to try and trace out the circuit in this area by following the tracks and find out what this component actually does. Looking at your photo it looks like this resistor is in series with C177. Is this capacitor good. Might have gone short-circuit. But there might be more tracks that we can't see. So check carefully. Report back when you know more.
     
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  7. Alec_t

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    Sep 17, 2013
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    My colour vision is poor, but I reckon the left-most band is red and the right-most is gold.
     
  8. MikeML

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    Oct 2, 2009
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    Looks like Brn-Brn-Blk to me (11Ω) ...

    res.gif
     
  9. studiot

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    Nov 9, 2007
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    Well spotted.

    As a result make sure there are no sharp bits when you resolder the new one in and keep it slightly raised off the board.

    Yes I agree from mike's photo, 11 ohms.
     
  10. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    11 ohm is not a typical value, so my guess would be brown-red-black that gives a standard 12 ohms. Or it could be red-red-black that gives 22 ohms.
     
  11. crutschow

    Expert

    Mar 14, 2008
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    If you look at the original picture of the burned resistor, I think the first band looks more red than brown.
     
  12. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Dobri Den,

    Since the last band in the OP's photo is gold, then 11Ω is a standard value in the 5% line up.
     
  13. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    It could be red-red black, wich is 22 Ohms, a standard value.

    Bertus
     
  14. wayneh

    Expert

    Sep 9, 2010
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    I'd remove it from the board and take a look at the other side. It might not have gotten quite as hot.

    It looks more red to me than brown.
     
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