How To Find Burnt Resistor Value?

Discussion in 'General Electronics Chat' started by Tolerance, Jun 4, 2009.

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  1. Tolerance

    Thread Starter New Member

    Mar 18, 2009

    As a maintenance tech. I'm facing a problem of a burnt resistor, such burning that made the color bands fade out. so my question is :'How To Find Burnt Resistor Value'

  2. Mike Mandaville

    Active Member

    May 27, 2009
    I used to make my living as an electronics maintenance technician, and I never worked on any circuit for which I did not first acquire a schematic diagram. Therefore, my advice to you is to first acquire a schematic diagram, and then just look at the pretty picture.
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    In addition to the above, with experience, you can sometimes make a good guess as to the correct value. But that usually involves finding the reason for the component burning in the first place, so you will have made a partial schematic of the failed part of the circuit.
  4. BillB3857

    AAC Fanatic!

    Feb 28, 2009
    If you ALWAYS had a schematic for circuits you worked on, you truly have led a charmed life! In my job at a small industrial service company, a schematic is a real treat. Most of the equipment we see is composed of obsolete designs our customers want to keep running rather than spend capital money to replace. If we are luck, we may be able to get an interconnect drawing from the customer that will show how the board in hand is connected to outside circuitry. Manufacturers of industrial equipment have become very protective of their designs and information. Most respond to a request for a schematic with, "Send it to us. We'll fix it." Other companies that once freely distributed schematics with the purchase of their equipment no longer do so. The problem seems to have been on the rise as the once tech friendly companies are being bought up by larger companies. Larger companies have the luxury of going to a component manufacturer and saying, " I want to buy 10 million of your 74LS00 ic devices but I want you to ID them as XYZ-098." That pretty well defeats an attempt of repair outside the OEM affiliated shop.

    Reverse engineering seems to be the order of the day.
  5. Tolerance

    Thread Starter New Member

    Mar 18, 2009
    Thank your for your NO HELP.

    Yes in ideal world this is the case and I knew it 20 years back, but please I asked a real life help, the day you face it, answer others questions, else, 'if have nothing to do, don't do it here' I know my ABC.
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    Interesting choice of username you selected.

    Unfortunately, life is like that. in past years, we all had schematics to work off of. That eliminated the guesswork. Without such an aid, it is guesswork. There is no magical ritual you can perform to get the value of the resistor, any more than guidance to the failed component that caused the resistor to burn.

    You work out the schematic from the circuit and, using experience, try to guess the value for the resistor - always assuming you have found and corrected the real problem.
  7. eblc1388

    AAC Fanatic!

    Nov 28, 2008
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    I love the way you asked for help without providing ANY info re the size/look of the resistor, what appliance it was in, where it was in the circuit, what caused it to burn, or ANY other info that might have allowed the experienced repairers here to help you determine the value of the resistor. :(
  9. Mike Mandaville

    Active Member

    May 27, 2009
    Tolerance, that should be "Thank _you_ for your NO HELP".

    Tolerance, that should be 'in _an_ ideal world this is the case".

    Tolerance, that should be "I asked a real life _question_"

    Tolerance, I did answer your question. You just didn't appreciate it.

    Tolerance, that should be "if _you_ have nothing to do, don't do it here".

    Wonderful. Now how about learning some BASIC ENGLISH, and some COURTESY as well.

    Mike Mandaville
    Austin, Texas
    Šamaš-šum-ûkīn likes this.
  10. bertus


    Apr 5, 2008

    The value of the resistor is dependent on the application.
    In what part of the circuit is it used?
    Why could it get burned?
    A schematic would certainly help.

  11. Salgat

    Active Member

    Dec 23, 2006
    Sorry but your last comment of your first post was pretty rude/condescending.
  12. Mike Mandaville

    Active Member

    May 27, 2009
    Sorry, but you have developed a misperception. Your speculation regarding my intention is outranked by the understanding that my answer fit the question. And that you can find something offensive about the word "pretty" says far more about you than it could ever say about me. Would you like to try again?
  13. Zenock

    Active Member

    Jun 1, 2009
    This is why I try to think three times before posting a response. Even then I have a tendency to screw things up. I can totally see where if I were Tolerance and I might have spent hours upon hours upon hours looking for a schematic and one just wasn't to be had (Don't know that he actually did this) then read Mike's response, my frustration level might go through the roof and I might become flustered while responding defensively and angrily.

    I can also totally see how Mike might not have meant anything by it and it was a simple interpretation missunderstanding. Mike not understanding Tolerance's frustration might be frustrated by his defensiveness and ager and might react to that.

    Now I'm not saying that this is what happend. I don't know why people do what they do or write what they write. When I read what they wrote even when I feel confident that I understand what they mean I wouldn't be surprised if it turned out I was wrong. But I do feel there is some tension here so if you are tense, remember that people are only trying to help and that your help is appreciated.

  14. Mike Mandaville

    Active Member

    May 27, 2009
    Yes, I have spent many a charmed hour sweating under a hot high-intensity lamp with a magnifying glass pressed flat up against my face reverse-engineering a piece of equipment in order to acquire a schematic diagram, or, since beenthere has already introduced the more precise term, a partial-schematic. Been there, done that.
  15. radiohead

    Distinguished Member

    May 28, 2009
    If you can get an identical board, you can determine the value of the resistor.
    NOTE: To expect professional help, it would be appreciated if you provided some technical information, a photo of the component side and solder side of the CCA in question. Don't come in here and ask a vague question then get all uppidy when you don't get the answer you wanted. Many of us have years of experience and are gracious to offer troubleshooting tips online for free.
  16. Engr Mick

    New Member

    Jan 29, 2014
    Below are 4 easy methods to find the value of burnt resistor...
    How to find The value of Burnt Resistor ( By three handy Methods )

    Method 1

    1. Scarp the outer coating.
    2. Clean the Burnt Section of the resistor
    3. Measure resistance from one end of the resistor to the damaged section
    4. Again measure the resistance from damaged section to the other end of the resistor.
    5. This is the approximate value of Burn resistor
    6. Just add a small value of resistance for damaged section .i.e., suppose the value of burnt resistor was 1k Ω, but you got 970 Ω. So just add 30 Ω, and you will have 1k Ω.
    Gdrumm and colinb like this.
  17. paulktreg

    AAC Fanatic!

    Jun 2, 2008
    Engr Micks method has worked for me in the past, it can get you close to required value but please scrape rather than scarp! :)

    If you can give us a little more information about what you are working with it would help although I do appreciate manufacturers don't like to release schematics these days.

    Forget the MAD comic character, he likes to use long words, presume your first language is English and that nothing ever gets done if a schematic isn't available and if as another new member I completely understand if you never come back! :(
  18. Wendy


    Mar 24, 2008
    Congratulations, you have practiced the arcane art of necromancy, the revival of a long dead thread. Likely the OP (Original Poster) has solved his problem in the years that has passed, or thrown it away, or something.
    BMorse likes this.
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