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How to Test a DC Jack?

Discussion in 'Electronic Repair' started by [email protected], Jul 20, 2005.

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  1. Guest

    Greetings,

    when the DC jack on my Sony Vaio FXA32 broke, I got the motherboard out
    and soldered in a new jack. Put the MB back into the case, plugged it
    in, attached the LCD, and it POSTed. Happily I re-assembled the laptop,
    only to find that in order for the adapter to power the laptop, I had
    to push it in and hold it tight. After a while that stopped working,
    too.

    The unit runs fine off the battery, so I haven't fried anything. But
    how do I find out what the problem is now? Is it the replacement jack,
    or the way it's been soldered in? It looked fairly straightforward, and
    the fix did work the first time...

    Thanks,

    Yisroel
     
  2. Sure you got the right type? I've come across ones with the same OD to the
    plug - say 2.1mm - but the centre pin ain't the same size on both. Might
    be worth getting a plug from the same source and changing that too.

    Hate the things. ;-)
     
  3. It also might be just a shade shorter or something and you are working the
    plug against the case to get it in far enough.

    WT
     
  4. mike

    mike Guest

    I don't have any experience with that exact model.

    But plugs rarely break. What breaks is the connection to the board.
    You may still have cracked traces that disconnect when flexed.
    Did you use the EXACT replacement part from sony.
    Slightly different inner/outer diameters can cause what you experience.
    Are you sure the problem wasn't in the plug end? Plugs get more flex
    and the wire tends to break right at the end of the strain relief.
    mike

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  5. Ross Herbert

    Ross Herbert Guest

    As has been hinted in this thread, the dimensions of the replacement
    socket and pin most likely do not conform to those of Sony plug. It
    has been my experience that laptop manufacturers almost invariably use
    OEM specific connectors for the DC input plug and socket which do not
    match the ones commonly available in electronics parts stores.
     
  6. jakdedert

    jakdedert Guest

    In addition to the suggestions already made, be aware that the circuit board
    in your laptop contains many layers. Each has it's own traces (conductors).
    Think of a regular double-sided circuit board (conductors on each
    side)...then imagine two or three of them sandwiched together, with some
    components (like the power jack) needing to be connected to traces on more
    than one layer. It's sometimes a little more difficult than soldering just
    the conductors you can see, although, ideally each such hole should be
    'plated through'; meaning the inside of the hole has it's own layer of
    copper and connects to each layer.

    You might have missed one layer, and when you hold the plug 'just so' it
    makes mechanical contact.

    jak
     
  7. Guest

    Many thanks to those who responded.

    Dave and Wayne, I checked the prongs on the jack with the AC adapter
    plugged in. It does supply the voltage, so the jack *is* compatible
    with the adapter. (I should've done this first.)

    Mike, it *was* the jack that broke - the plastic receptacle for the
    center pin just disintegrated into shards.
    This sounds like the most likely culprit. The ends of the prongs that
    stick through the board I have soldered solid, but that doesn't mean
    that there's contact inside the board. Damn. Guess I'll have to get the
    thing out and try to plate the insides of the holes with solder or
    something. Oh well...

    Yisroel
     
  8. jakdedert

    jakdedert Guest

    I only put it out there as one likely culprit along with the suggestions of
    the other repliers; but it's worth investigating.

    jak
     
  9. Dewaine Chan

    Dewaine Chan Guest

    Use a MultiMeter to ring it out before you put it all back together. Another
    thing to watch out for is you accidentally heated up a component near by and
    made it loosen up. Been there and done that.

    Dewaine
     
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