SMT identification, MoBo repair

Discussion in 'General Electronics Chat' started by whi5p, Apr 8, 2005.

  1. whi5p

    Thread Starter New Member

    Apr 8, 2005
    Wow, this forum took a while to find but I'm glad. Looks great.

    My problem is an AU13 motherboard I just bought off ebay.
    While installing the heatsink retaining clip, you guessed it!
    Anyway my tool ground a tiny surface mount device to dust.
    I can afford to replace the board, but would think a repair is
    within my capability (I am a pretty good with solder)

    this device is right off the processor, and close to the Northbridge.

    It was labeled L14, which my buddy tells me is probably
    an inductor. Anyway, there are several other Lxx components
    nearby, all alike so I have been trying to make a visual
    match from scavenged parts. unsuccesful so far.

    This device has no markings of any kind that I can see under
    a magnifying glass. Having looked at several circuit boards
    for something to solder in for testing I notice that lots of
    SMT surface mount devices do in fact have no numeric
    markings. So. . . .

    How does one identify these devices?
    It seems there are lots of SMT SMD devices that do not
    have numeric markings.

    I have been searching the internet (including your usenet
    archive) for hours now about color codes, packaging, "no mark"
    SMT devices and have come up pretty empty.

    Can someone direct me to a guide for identifying these devices
    inductors in my case, but also Capacitors and resistors that have
    no numeric markings, (no mark , no label , for the indexer)
    I'm guessing it will have to be color and packaging.

    Also, if one can think of a supplier like mouser or even a little
    assistance in getting a match from a scavenged board, I would
    be flabergasted in my appreciation. (like match the color first
    then the package size, or vice versa)

    thanks anyway!
  2. mozikluv

    AAC Fanatic!

    Jan 22, 2004

    they have numbers printed on the surface which represents the code. most or some of this smds are mounted upsidedown. that's why you don't see the number code. :( as to your inductor there are color bands on it.
  3. whi5p

    Thread Starter New Member

    Apr 8, 2005
    thanks for the reply Mozikluv
    unfortunately, I'm still observing components that don't seem yet to
    fit into your description. I just want to identify what this "L" component
    is and replace it, and so I've been looking around trying to learn a little
    bit about identifying components and have run aground in my research.

    This is probably because I'm looking at consumer
    mass market cheapo electronic boards? One is the board from a cdrom.

    For instance, every one of these components I've removed from scrap boards
    has had no markings on it of any kind, including the bottom/sides.
    I am using a magnifying glass but will be looking at them this weekend under
    a scope.

    they each appear to have individual colors, but no bands that I can tell.
    I have various sizes, all oblong boxes with solder ends. Dark grey, light grey,
    and a yellow brown. just one color between the solder ends.

    Am I to understand that these colors define something? Can someone give me a decent
    search term to look up a guide on identification?

    I have a dmm and access to an oscilloscope, so being able to measure inductance is a possibility for me (?). Also, this is an athlon/nforce 2 chip connect so I believe I might
    get data from that as well but it might involve removing heatsinks from the nforce2 chips.

    Thanks again for the help!
  4. mozikluv

    AAC Fanatic!

    Jan 22, 2004

    i understand your predicament of not being able to identify values due to intentionally erased part #s. i have encountered some of those and it's really frustrating. :angry:

    your test instrument will be of no use if the part you are testing is busted. if the part use is of good quality even if they try to erase it there would still remain traces of the part number you just have to a good lens. but most of the time they scrub it quite well.

    you can try to have the schem or look at the same working condition board.

    those bands are read like resistors and here's a chart for inductors
  5. whi5p

    Thread Starter New Member

    Apr 8, 2005
    The inductor chart is definately handy!
    I just went to thier site and it seems I've already seen
    most all of thier help pages.
    I should note that it does not mention surface mount
    devices, but pictures a device with leads for through hole mounting, etc.

    So you say they scrub the markings off?
    All the way around so all the banding is removed?

    These devices are TINY! Surface mount device the size of a
    few poppy seeds.
    I am not convinced yet that these devices were scrubbed off.

    Anyway, there are more devices on the board I can remove and
    test. They are visually identical to the one broken.

    Honestly, I appreciate the help but it seems like I'm being
    needled and having a joke played on me. Are you seriously
    telling me a tiawanese manufacturer scrubbed the markings off????
  6. mozikluv

    AAC Fanatic!

    Jan 22, 2004

    i will not be specific as to what country that mostly does that style of erasing the markings. but here in asia there are so many manufacturers who subcontract works to small companies. refutable companies do not erase the part # they use, only the dubious kinds do that. the reason behind they do it because they do not use reliable parts.

    3 or 4 pin smd transistors are usually mark 1A, 1L or 1G and others like GA, GB are codes used by the manufacturers. that's why it's important to know who the manufacturer is. i believe this kind of marking has not yet been standardized. i hope someday they do it like the regular transistors.

    smd inductors have markings if they come from refutable manufacturers. if it had been erase then we can partly conclude that the body was made of plastic and not the ceramic type where you cant erase the marking coz if you do so you would also destroy the smd. ;)

    another tip in checking the type of board used if they come from a refutable company. the dubious board is more pliant than the good kind. ;)
  7. whi5p

    Thread Starter New Member

    Apr 8, 2005
    thanks for your insights Mozikluv.
    I am in chicago usa :)

    I guess I'm not unaware of sub standard parts and practices,
    nobody usually ends up looking into it and just want
    CHEAP CHEAP CHEAP on the price.

    Just for documentation here on the list
    I believe these inductors were ceramic.
    I original board was produced by FIC or First International Computer
    who I have a decent history with.

    The scrap board I was using to grab parts from was from
    a Ricoh cdrom drive.

    by the way I think you mean "reputable" but then again
    my only other language is spanish and it is not perfect!

    You english is pretty good :)
    and thanks again for the help.
  8. mozikluv

    AAC Fanatic!

    Jan 22, 2004

    i believe i have used the right word "refutable" because i question the integrity of those dubious companies. those dubious companies have reputable character. ;)

    anyway am not a master of english, just know a little spanish, japanese and french :D