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Most common failure survey.

Discussion in 'General Electronics Discussion' started by Tha fios agaibh, Dec 11, 2015.

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  1. Tha fios agaibh

    Tha fios agaibh

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    I know its impossible to say specifically because circuitry and components vary widely, along with the conditions and applications.
    But, generally speaking;
    Is their one type of component or failure that you see most often in electronic repairs?

    Example, leaky electrolytic capacitors, shorted/open diodes, failed transistors, bad solder joints or connectors, op amps, etc...
     
  2. davenn

    davenn Moderator

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    #1 -- would be leaky electros
     
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  3. Martaine2005

    Martaine2005

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    John,
    That's a really good question, one I often ask myself!.
    I can probably get the conversation going by adding:
    Caps..= most things old!, power supplies, most things!
    Amps = output transistors.
    Anything else in between.

    Martin
     
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  4. Martaine2005

    Martaine2005

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    Also , diodes...
    Because of wrong polarity....A very simple internal pcb fuse is also 80% the problem.
     
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  5. Tha fios agaibh

    Tha fios agaibh

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    What do you define as old for circuits?
    Caps >20 years old?
     
  6. Martaine2005

    Martaine2005

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    Oooh, another good question....
    Totally depends on the use! Somewhere hot will dry it out quicker. Others might skimp and scrape on the voltage and kill it! Example: A 12v circuit with a 16v cap. Better to use a 25v or higher cap..

    Martin
     
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  7. Arouse1973

    Arouse1973 Adam

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    Bad designs can give components a bad name. But yes elects are bad boys. But then you have circuits using them that last over 20 years. It depends on their rating and if the designer under rated them.
    Adam
     
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  8. Arouse1973

    Arouse1973 Adam

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    Yes 20 years or more for me.
     
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  9. Minder

    Minder

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    Old tube stuff mostly capacitors, in reviving antique car radios, its a given to replace all the caps regardless, the non-electrolytic were mainly wax paper.
    M.
     
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  10. Martaine2005

    Martaine2005

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    Yes but no but John.....
    20 years is for older designed caps....
    Mine last 3 days after the warranty runs out !! Max 3 years..:)
     
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  11. Tha fios agaibh

    Tha fios agaibh

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    Sounds like about 75% of the time you see bad caps?
    (Aside from fuses or switches going).

    Reason I ask;
    I'm at a beginner's level as far as repairing circuit boards. I shy away from complex circuits and ones that have a lot of smd components.
    My fear is investing the time and money on replacement parts, only to find there is a failed IC like a microcontroller or other unidentified part that I'm unable to diagnose. To add to confusion, schematics are often impossible to find.

    How often do you do the obvious repairs only to find that a controller or a processor chip is toast?
     
    Last edited: Dec 12, 2015
  12. davenn

    davenn Moderator

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    depends a lot on the circuit the electros are in

    for power supplies and other higher temperature situations, its lucky to get 5 yrs out of electros
    and in those situations I definitely wouldn't trust any electro of around that young age
     
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  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Electrolytics in switch mode power supplies (high stress).

    Diodes across the output of power supplies (people connecting batteries the wrong way when trying to charge them).

    Output transistors in amplifiers (when people short the output).

    Fuses (in any of the cases above).

    Leaking batteries (and subsequent damage).

    Regulators (when people connect the input power backwards -- if you're luckier it's a diode instead).

    Operator who can't read (or doesn't have) manual.
     
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  14. dorke

    dorke

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    That has to do with the Taiwanese capacitor plague .
    If you have a genuine cap from a respected company it can last much longer.
     
  15. dorke

    dorke

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    It is quite rare.
    In cases it does happen it is very likely the all board is toasted.
    That mostly happens because of :
    1.Mains power surge.
    2.Power supply failure,such that creates a VCC above ICs max absolute value.
    3.Lightning.
     
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  16. dorke

    dorke

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    One to add to the list:
    Rubber bands !
    In motor driven equipment(DVDs,CD players,VCRs,Tapes etc.) they are the number one problem.
    With time they dry out...
     
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  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I think that is actually a little overblown. The onset of the problem started at about the same time as motherboards started including their own switch mode regulators for the low voltage rails. The stress on the caps due to the high ripple currents had an awful lot to do with it.

    Sure, lower quality caps didn't help, but the problem was far too widespread for the apocryphal reason to be the whole story.
     
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  18. Martaine2005

    Martaine2005

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    I hear you!
    My Toyota Previa used to cut out when idling, Toyota had it for 5 days and finally rang me with an estimate. £1350 for a new throttle body, two injectors, Erv or EG valve or something?
    I refused and got a second opinion from a chap that does a "no cure, no fee". £35, to tell me the fuel pump!!
    I changed it myself and never had another problem!!

    So it's not just electronics! All Techs start with what they think and slowly delve deeper. Never once removing the new part that was not needed..

    It should never be a fear of wasting time! It's the enjoyment of repairing something.. (Unless it's your work)...Then it is time, unfortunately.

    Martin
     
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  19. davenn

    davenn Moderator

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    accounts for some but not all heat related failures ;)

    totally agree with Steve's comments above
     
  20. davenn

    davenn Moderator

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    you must work on different gear

    in domestic electronics it is VERY common, 60 - 75% would be a fair percentage
    and they fail quite happily on their own WITHOUT any prompting from any of your 3 reasons
    replace the caps and it works again immediately without any other component replacements


    Dave
     
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