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Please recommend instruments and help for circuit board troubleshooting.

Discussion in 'General Electronics Discussion' started by Rhett35, Mar 27, 2013.

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  1. Rhett35

    Rhett35

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    Mar 27, 2013
    Anyone please help recommends an instrument for circuit board t-shooting down to components level. I am planning to have my own electronics repair shop...thanks a lot.
     
  2. CocaCola

    CocaCola

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    Apr 7, 2012
    A good multimeter is a great start, followed by an oscilloscope...
     
  3. Rhett35

    Rhett35

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    Mar 27, 2013
    Thanks but i have that instruments already....think better say "advance" instrument for circuit board troubleshooting...thanks
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    If you're planning to work on boards with switch mode power supplies (which means almost everything these days) an ESR meter would not go astray. They can give you a quick go/no-go test of filter capacitors in-circuit.

    The other thing is *lots* of bench space.

    Perhaps a rugged bench power supply capable of powering equipment where the power supply is possibly at fault.

    An extension cord that has a series light bulb fitted. (not exactly "advanced")
     
  5. CocaCola

    CocaCola

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    Experience and know how, those 2 devices will allow for most general diagnostics... If you need specialty equipment for a particular type of circuit well that is specialty and will depend solely on what you need...
     
  6. Rhett35

    Rhett35

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    Mar 27, 2013

    I've heard about this light bulb method in tshooting smps power supply...can you share any useful links for this? thanks...
    For ESR, is it possible to use this when capacitors on board? or you need to remove the capacitor and measure...thanks guys.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The "dim bulb tester" technique is useful for lots of things.

    It relies on the fact that a bulb has a lower resistance when cold than when hot (it's like a huge PTC protection device)

    At low currents it drops very little voltage, but as the current drawn by the device gets closer and closer to the rated current for the bulb, the voltage available to the device under test drops more and more. Effectively it limits the power dissipation in the device under test to a lower (and hopefully safer) value allowing you time to troubleshoot before semiconductors expire or fuses blow.

    ESR meters can normally be used in-circuit because they typically place a very low voltage (around 100mV) across the capacitor, so it's not going to be affected by diode junctions and resistors in the circuit are almost always going to be far higher than the expected value of ESR. If you have many capacitors in parallel, the ESR meter can measure low, but you should be aware of that and multiply the result by the number of capacitors. You'll need to remove (at least 1 lead of) them to test them individually though.

    It's a truism that knowing how to use the equipment you have properly will almost always yield better results than getting more equipment. For example, your oscilloscope can be used to estimate the ESR of capacitors (but it's not really convenient in most cases)
     
    Last edited: Mar 27, 2013
  8. Rhett35

    Rhett35

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    Mar 27, 2013
    Still confuse the bulb tester technique...do you have links to share about this?
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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  10. davenn

    davenn Moderator

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    his comments and questions so far would indicate that those 2 things are severely lacking in his inventory ;)

    Dave
     
  11. RHeTTRoNiCS

    RHeTTRoNiCS

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    Mar 28, 2013
    Components Level Circuit board troubleshooting...

    Guys i need your help...i got a new job as a pcb troubleshooter. I have an experience about that (but not expert)...this new job some stuff also don't have a schematic...Just like 3rd party repair...I believe i need to improve my skills in t-shooting at components level. Like how to check the following components in-circuit:
    1.) IC
    2.) Caps
    3.) Resistor
    4.) Inductor
    5.) Mosfet/Transistor
    6.) Diode
    7.) Transformer

    Please share any links, ideas, or info...thanks guys...
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    First we need to know what you're employed to do.

    Are you looking at boards that have failed QA immediately post manufacture?

    If so, I would be looking for missing components, missing solder, tombstoned components, incorrect placement, solder bridges, etc.

    If you're dealing with equipment returned as faulty from service then you will probably be able to ignore most of these.
     
  13. CocaCola

    CocaCola

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    Apr 7, 2012
    Last edited: Mar 28, 2013
  14. davenn

    davenn Moderator

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    Good question. Hope there's a good answer
     
  15. RHeTTRoNiCS

    RHeTTRoNiCS

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    Mar 28, 2013
    I'd like to change the username..that's all....i will never use the old one...this is my new account.
    I work in a vendor company which troubleshoot faulty units out from production equipments. Most of the time my boss gives me unit to repair that i'd never been before...These are without schematic units so i need to t-shoot at components level...Let me know if there's more questions..thanks a lot.
     
    Last edited: Mar 28, 2013
  16. CocaCola

    CocaCola

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    Apr 7, 2012
    Fully dependent upon the IC and it's function...

    LMGTFY

    See #2
    See #2
    See #2
    See #2
    See #2

    There really is no use for us to copy and paste or retype what has been covered many times over already and can easily be found in a Google search...
     
    Last edited: Mar 28, 2013
  17. davenn

    davenn Moderator

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    didnt quite merge the way I wanted the threads to but it will do :)

    Dave
     
  18. GonzoEngineer

    GonzoEngineer

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    Your boss is a Jerk! How in the hell does he expect anyone to troubleshoot to component level without a damn schematic?
     
  19. RHeTTRoNiCS

    RHeTTRoNiCS

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    Mar 28, 2013
    Guys i did my assignment lastnight, got some "not much" info on t-shooting the parts and wanted to share also:
    1.) IC --> Look for the datasheet and check pin configuration. Read all pins by diode test and ohm with respect to ground. If found low-ohm , trace and t-shoot...nothing more we can do.
    2.) Caps--> Measure with LSR. Suspect those caps if reading is lower than the value..
    3.) Resistor --> Ohm out the resistor. Suspect those if reading is higher than the value..
    4.) Inductor--> Check for continuity only.
    5.) Mosfet/Transistor --> Diode test all pins...suspect bad if read <0.1...ALso can power up the unit and measure gate voltage. If no g-voltage, the supply for g-voltage might have the problem. If have g-voltage, drain-soure ohm out should reduce...(i need more research on this.)
    6.) Diode --> use multimeter diode test. readin should not the same in forward and reverse.
    7.) Transformer--> Primary and secondary should be very high ohm. Otherwise, might have some shorted windings...

    I need more research and study....thanks..
     
  20. duke37

    duke37

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    Jan 9, 2011
    7. Transformer.
    For efficiency, the windings should be low resistance. You will need to find the normal resistance and see if you component is within say 5%.

    Shorted turns may not drop the resistance much. Say you short 10 turns in a 1000 turn winding, that is only 1% but could have a disastrous effect on the inductance.
     
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