IC identification and testing project

Discussion in 'The Projects Forum' started by AJMetal87, Mar 27, 2014.

  1. AJMetal87

    Thread Starter New Member

    Mar 15, 2013
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    Hey guys. I am in the process of familiarizing myself with the different types of IC's and how to troublshoot each of them so I can test other PCBs for defects. I have attached an image and I was just hoping to get some insight on the green and red circled IC's.

    If someone could assist me in identifying these IC's, I could then google how to actually test them. I think the red guys are diodes, but I am unsure if they truly are because they look different than some of the other diodes on the board.

    Thank you in advance for the help guys.
    [​IMG]
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    red = diodes
    green = inductors
     
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  3. AJMetal87

    Thread Starter New Member

    Mar 15, 2013
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    Ok cool. Thank you!

    Please let me know if I understand the testing process correctly:

    Inductor can be tested by putting either lead on each pad of the inductor, if it beeps, it should still be good because current is able to pass through.

    Diodes - if I get a .001 or .0 reading with the diode setting on my multimeter, the diode is bad and needs replacing.

    Which brings me to my next question: The diodes I suspect that have gone bad are coded with "P03CM 8G2N5", however, searching that brings me to a bottomless pit of alibaba. Is there a way to figure out what the values of the diodes were without having schematics or a working version of the same board?

    I am Assuming these IC's can be dependably tested while in circuit.
     
    Last edited: Mar 27, 2014
  4. mcgyvr

    AAC Fanatic!

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  5. wayneh

    Expert

    Sep 9, 2010
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    The parts with the polarity marking: How can you be sure those are not capacitors? Maybe your eyes are better than mine.
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    I vote for electrolytic capacitors. Multimeter behavior will vary, but putting the probes across a capacitor will charge it up and produce nonsense looking results.

    I have a question back at you. What does the internet say about the difference between testing a component on a circuit board and a component that is all by itself? The reason I ask is that you will get different results. Without understanding the circuit you are troubleshooting you can actually make the damage worse.

    Static discharge is particularly insidious hazard which may weaken a chip in a way that will cause it to fail 3 months later. Those are a bear to troubleshoot.
     
    Last edited: Mar 27, 2014
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  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Good catch.. I just glanced at them..
    The ones with the (+) mark are probably caps..
    The other 2 without the + are diodes.. The faint line on one side is the cathode band..
     
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  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    The ones with white writing are tantalum caps, size "B" and "C" packages. The marked number is uF, so 47 = 47uF, and 100 = 100uF.

    The two smaller ones are high speed rectifier diodes, probably schottkys.

    All the round ones are inductors.

    If you really want to test/repair that circuit the main thing to do is power it up and check the voltage rail test points that are clearly marked. If the voltages are ok, it's working. :)
     
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  9. AJMetal87

    Thread Starter New Member

    Mar 15, 2013
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    I appreciate the help guys, I am still in the process of troubleshooting this guy, but I will keep you in the loop.

    In effort to avoid creating a new post I have a follow up question you guys may be able to assist with.

    If a piece of networking equipment (cell site subscriber module or point-to-point back-haul etc) is testing with a ping that is all over the place (1ms to 1700ms inconsistently), is there a specific IC that would be your first 'goto'?

    Or maybe this is a better way to phrase it: Which IC's regulate ping?

    I have a rework station and can re-ball, re-flow BGAs (most of them on the equipment I am working on are CPU's and transceivers).

    These units are outside and must withstand the elements, fractured solder joints/balls are not an uncommon occurrence that is easily fixed with my oven, iron, or rework station.

    I will also add that I am still in the beginning of understanding the fundamentals of electronics. Most of the repairs I have done thus far give me a physical sign of where the defect may be. discolored IC, fractured joint (20x to 40x magnification needed) etc.

    With that being said, I apologize in advance if my questions or verbiage seem ignorant or common knowledge to an educated engineer.

    I do not have any schematics for the equipment (mostly propriatary Motorla/Canopy and Alvarion units), which would inevitably make troubleshooting a breeze.
     
  10. burger2227

    Member

    Feb 3, 2014
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    Welcome to the club! I've never seen capacitors that looked like that either... ;)
     
  11. AJMetal87

    Thread Starter New Member

    Mar 15, 2013
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    Oh boy, If I took a few pictures of the pcbs that get brought to me daily for reflow/reball youd be amazed. my primary job is reflowing/reballing volume daily in attempt to repair networking equipment ranging from $30-$15,000. these boards are insane.

    But yes, hence my original question, I am looking to expand my knowledge to troubleshoot more difficult issues and Allaboutcircuits has provided me with a plethora of knowledge. I love the resources this community has to offer.
     
    Last edited: Mar 28, 2014
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