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Flyback transformer?

Discussion in 'Power Electronics' started by TonyRepairKe, May 20, 2019.

  1. TonyRepairKe

    TonyRepairKe

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    May 20, 2019
    Initially my crt tv was powering with sound ok but no screen black. I replaced a popped cap 126/4.7μF with 126/47μF...the screen was now blue ok...but later sound got lost and the screen became black once more.....could the flyback have fried, pls help
     
  2. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    I don't know what 126 is, but a 4.7uf cap shouldn't be replaced with a 47uf.
    Sounds like you've fried some discrete component(s) rather than the flyback coil.
     
  3. TonyRepairKe

    TonyRepairKe

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    May 20, 2019
    Thanks for your reply.....with your vast experience ...what discrete components in your seem to have gone malfunctioning.
     
  4. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    What is going on here? It appears to me that @TonyRepairKe has ZERO qualifications to repair any type of electronics, and most especially NO qualifications to repair anything as ancient and sophisticated as a crt television. Most of these are in landfills by now for very good economic reasons.

    Components have specific values and characteristics for reasons that depend on how they are used in circuits. You cannot, willy-nilly, substitute components of different values and/or characteristics and expect the substitution to work in the same manner as the original component. Whether your substitution resulted in a "fried" fly-back transformer requires troubleshooting skills to determine.

    While certain components, such as hermetically-sealed electrolytic capacitors, can often be visually identified as failures through ruptured seals and leaking electrolytes, simply replacing such failures does nothing to isolate and determine the cause of the failure, which could range from simple "old age" as some components do age and wear out, to over-stresses caused by other malfunctioning circuit components.

    It is the essence of troubleshooting to discover the why of failure, not just what failed. We don't teach troubleshooting here. This is NOT a teaching forum, it is a mutual self-help forum where members share a common knowledge of electronics and help each other through a conversational dialog.

    So, @TonyRepairKe, what qualifications do you now possess that would lead you to believe you can troubleshoot and repair a crt television? Have you taken and passed any courses in television repair? Do you know anything about electricity or electronics?
     
  5. TonyRepairKe

    TonyRepairKe

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    May 20, 2019
    One thing i am a beginner this thing about CRT tv sets.... You are being too harsh on me,but i hope you can share on what could have went a miss here. Thanks
     
  6. TonyRepairKe

    TonyRepairKe

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    May 20, 2019
    One thing i know is discrete components include Resistors,diodes,capacitors,transistors etc.
     
  7. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Does it appear that I may have hurt your feelings, Snowflake? Maybe. I am just a crotchety old man, but I learned to identify incompetence a long time ago. I have zero tolerance for incompetence because it is a huge waste of time and money for everyone involved. I asked three questions of you in the last paragraph of my post #4 to see whether or not we have any common ground for discussion. Apparently we do not, as you did not reply to any of my questions. So, you can continue replacing parts, and hope that eventually you will stumble across whatever component (or components) is causing the problem. I have no suggestions as to which parts are likely candidates to fail first.

    Back in the day (1950s) TV repair shops often took this approach, swapping out vacuum tubes for brand-new ones until the problem went away. The only reason this sort of thing sometimes worked was the high failure rates for vacuum tubes. Laws did not allow a brand-new tube that didn't solve the problem to be returned to its box and sold to someone else as a new, un-used, tube while the original (non-defective) tube was returned to its original socket. No, the customer was charged the full (i.e. inflated) price for the new tube, which was then allowed to remain in the television set although it contributed nothing to the repair. For awhile, the sale of vacuum tubes was a major portion of the income for some radio and television repair shops, as well as for some drug stores who offered "free" tube testing machines. I suspect these tube testers were specifically designed to sell replacement tubes rather than to identify truly defective tubes, although of course burned out filaments, gassy tube envelopes, and decreased thermionic emission were all easily detectable.

    It generally requires years of study to become even moderately knowledgeable of electricity and electronics. Somewhere along the way the budding technician may begin to acquire troubleshooting skills, if they are capable of critical thinking. Many do not, and so they eventually leave a profession they were never fully a member of, to pursue something else they might be good at. Others hang on for years, replacing parts without understanding what they are doing and causing needless expense to themselves or <gasp> their customers. Shade tree, weekend, auto mechanics generally fall neatly into this category. Just because you may own a set of tools doesn't mean you know how to use them, or how to use them to diagnose problems and repair defective parts. That is what trade schools and apprenticeship programs prepare people for. Or if that isn't a suitable route for you, find a mentor and begin a self-study program. You can often find mentors at makers faires if you develop the people skills to reach out to them. Good luck!
     
    Last edited: May 22, 2019
    bushtech and Tha fios agaibh like this.
  8. Tha fios agaibh

    Tha fios agaibh

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    It's not a problem not understand something. One can usually learn to understand.
    What can be a big problem is when ignorance causes one to blindly do things that can lead to bigger and often irrevocable problems.

    In electronics repair, one must take a methodical approach and understand the circuit and behavior it exhibits using appropriate test equipment.

    It's of no use to replace one component if another nearby component is bad because your replacement has likely just failed again.

    Replacing components with other than the same specs will only cause further problems.

    Obviously, working on circuits that involve high voltages can be dangerous. The flyback transformer reaches up to about 30,000 volts. If one doesn't understand where these dangerous areas are, and have respect for the circuit, you can get knocked on your arse or killed.

    There is no way to say exactly what component is bad without knowing the circuit.
    You could post a schematic diagram along with your questions, but the best place to start is to do some reading on your own in order to understand the fundamentals of electronics.

    Good luck.
     
    hevans1944 likes this.
  9. TonyRepairKe

    TonyRepairKe

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    May 20, 2019
    Apprechiation, budding technichian,thats where i can say we are,i must apprechiate now troubleshooting rather than swapping.
    Thanks much,be sure i will get back to you when i want a headstart somewhere.
     
  10. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Swapping does play a role in troubleshooting, but only after troubleshooting has narrowed down possible causes of failure to several candidates. Unfortunately, it is often impossible to remove a component without seriously damaging it, or the circuit board on which it is mounted, so troubleshooting time spent to determine if a component is actually bad before swapping it is time usually well spent.

    That is one reason why the never-ending search for in-circuit testers is popular, especially for expensive or hard-to-remove-for-testing components. Personally, I don't much trust so-called in-circuit testers because many are affected by other components connected in parallel with the component or device under test (DUT). Since you eventually have to replace a suspect component anyway to verify (or not) that it is defective, you might as well (carefully) disconnect it and test it as a stand-alone, or simply substitute what you hope is a good replacement.

    Troubleshooting is a very difficult subject to learn how to do well. During your journey down that path, it would help if you would begin to keep a personal journal describing your experiences. It doesn't have to be a publishable work of art, just notes to yourself of what you have discovered that works, as well notes about what doesn't work. That way you can learn from your mistakes instead of repeating them.
     
  11. TonyRepairKe

    TonyRepairKe

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    May 20, 2019
    Am very greatful....tomorrow i will send a schematic of tv that has really squeezed my thoughts to the corner...Here in Kenya its 1945hrs, i will say goodnight.
     
  12. FuZZ1L0G1C

    FuZZ1L0G1C

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    Mar 25, 2014
    Taking the equation 1/(2piC), 47μ is 3.386 KHz while 4μ7 is 33.8627 KHz a big difference of 10x frequency / rolloff (or discharge time).
     
  13. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Isn't it 1/(2pi rc)?
    Yes, 10x anything is a lot.
     
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