How to determine value of inductor

Discussion in 'General Electronics Chat' started by Jotto, May 12, 2011.

  1. Jotto

    Thread Starter Member

    Apr 1, 2011
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    I have an inductor that burned up, which is part of the 12vdc main power. I don't have a schematic on this unit, so I don't have the slightest idea the value. The is feed right from the power supply to this inductor, and then on to the inverter for the inverter of a LCD. This is all surface mount devices.

    I can ring test them, but of course this is burned out and can't. What measurements must be taken? Frequency?

    Performed ring test on it, -0.5mh in circuit, of course it also suggests removal, this was performed on a working unit.
     
    Last edited: May 12, 2011
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
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    Unwinding and counting the wraps, measure diameter of the core, and wire gauge will get you pretty dang close.

    If you can re-use the core, (and there isnt 1,000,000,000,000,000 turns on it ;) ) you can have it re-built pretty quick.
     
  3. Jotto

    Thread Starter Member

    Apr 1, 2011
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    17
    Guess I should have listed its a smd device. Can't unwind that one.

    Thank you for your fast response, and sorry I didn't list that part. I have read about rewinding stuff, I have some very large transformers with my old tube amps I have. I have never tried this, but would like to one day before I am too old to see those large transformer.
     
    Last edited: May 12, 2011
  4. retched

    AAC Fanatic!

    Dec 5, 2009
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    Is there no markings on the inductor?
     
  5. Jotto

    Thread Starter Member

    Apr 1, 2011
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    17
    SMDs are very small now, it might be a 1/8 or1/16 of a inch long an 1/16 or 1/32 wide, not enough room to put anything. There are no drawings available for this unit, it was built my Smart Modular which doesn't make anything they just assemble the units. Parts are bought from others to make the monitor.

    Smart Modular was one of the companies producing LCD monitors for IGT. IGT dropped them after to many failures, which honestly weren't that bad. Power supply was junk, so my solution was just to put a desktop power supply in the unit, problems solved, and it was cheap.

    Ok, I do have a couple of working units that I just repaired, but as I said it must be removed for me to do a accurate check on the part, which is quite small and I would hate to drop it and then have 2 units down.

    Got the ruler out its almost 2mm long and 1mm wide. I have been contemplating just putting a piece of wire in that position. Its already broke, so not a lot to lose.
     
  6. Jotto

    Thread Starter Member

    Apr 1, 2011
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    Ok, decided to try a piece of wire and its been running for about an hour now.
     
  7. nbw

    Member

    May 8, 2011
    36
    10
    That's one of the things I find a little frustating with SMD - the small size is great for smaller boards etc but my old eyes, clumsy fingers make handling difficult... moreso if I can't tell what value component I'm trying to find on the floor! I'll always be a fan of the good 'ol resistor colour code :)
     
  8. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
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    It probably is a somewhat unnecessary part but it' s probably there to help prevent HF switching pulses from the unit getting back into the power supply.
     
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