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Need help recognising a component.

Discussion in 'Datasheets, Manuals and Component Identification' started by shady, Aug 3, 2013.

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  1. shady

    shady

    43
    5
    Aug 3, 2013
    Can someone help me to recognise this component. Is it a resistor or some sort of capacitor?
     

    Attached Files:

  2. davenn

    davenn Moderator

    13,837
    1,952
    Sep 5, 2009
    hard to tell
    its quite possibly a diode
    I have seen a number of SMD diodes marked this way
    if it was an inductor or a cap I would expect another colour band or 2
    are there any markings on the circuit board ?

    Dave
     
    Last edited: Aug 3, 2013
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    Yeah, I was searching for melf diodes with 2 bands as well.

    I would suggest you tale a few readings to determine if these show diode action.

    You might also show a bit more of the board, some context might help.
     
  4. dh390

    dh390

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    Jul 30, 2013
    It is very hard to tell but looks like there may be a black band on them as well. If you can take clearer pic with the flash on (you may need to try a few times to get a good shot that is not washed out) so we can better see the parts.
     
  5. shady

    shady

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    Aug 3, 2013
    It's a diode, no wonder my LCR meter was giving me strange readings.

    One way it was giving me around 500mV and the other side nothing so it has to be a diode. Also found one these diodes leaking on the board.

    Thank's for your help guys.
     
    Last edited: Aug 3, 2013
  6. shady

    shady

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    Aug 3, 2013

    Click on the second picture it's a lot clearer.
     
  7. davenn

    davenn Moderator

    13,837
    1,952
    Sep 5, 2009
    indeed :)

    as for the specific type of diode ... who knows ??
    you/we would have to see a schematic to get an idea of their purpose in the circuit

    Dave
     
  8. shady

    shady

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    Aug 3, 2013
    The board is from an electric forklift, it was passed onto me by a friend of mine to see if i could find any component failure. There is no schematics to it, can't find one. Here is the full picture of the board.
     

    Attached Files:

  9. shady

    shady

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    Aug 3, 2013
    The biggest problem i'm having is the lacquer on the board, it's hard to take off. I can use my hot air rework station or soldering iron but still a bit messy I'm going to try acetone I'll give you an update when the chemical has arrived. BTW it's a double sided board so there are tracks at the top and bottom of the board.
     
  10. techiesteve

    techiesteve

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    Jul 27, 2013
    I still use some very old HCK meter probes, they have very fine sharp points that will easily make contact through lacquer. Modern probes are often rubbish and can easily slip when probing components. In the past I used to repair boards that were used by our navy, they were lacquered for protection. We used a stubby brush and MEK to remove the lacquer or conformal coating, then replaced after rework.
     
    Last edited: Aug 4, 2013
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    My guess would be that they're a rectifier diode of some sort. There are lots of them and I guess they are used for input protection and suppression of spikes from switching inductive loads.

    Do you know what the fault is?

    I would probably start by checking all the "power" electronics before looking at the logic. Do the relays work? Do the switching transistors (or whatever they are) work?
     
  12. shady

    shady

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    Aug 3, 2013
    I just looked into MEK and looks good, might try that.

    Can you give me an example of the type of stubby brush you're referring to.

    I can't find any HCK meter probes here (UK) any recommendations?
     
  13. shady

    shady

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    Aug 3, 2013
    I've had a couple of these boards, so far i've found worn out caps, and a shorted transistor also a relay sounded as though it was sticking (not retuning to it's original position when you take the power off), that board is gone for testing after replacing the components. I got one left of those boards but I use that for spare parts.
     
  14. shady

    shady

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    Aug 3, 2013
    The highlighted areas is where I found the failed components.
     

    Attached Files:

  15. shady

    shady

    43
    5
    Aug 3, 2013
    With acetone and a firm toothbrush I've managed to remove the lacquer. Now it's a lot easier to read the components value.
     
    Last edited: Aug 10, 2013
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