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AC adapter hissing

Discussion in 'Electronic Basics' started by carpenoctem, Jun 23, 2004.

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  1. carpenoctem

    carpenoctem Guest

    Hey all,

    The plug on my old ac adapter broke a month or so ago. I have an acer
    c110. I went to fry's but they didn't have a suitable replacement. I
    bought a multiplug/multivoltage power adapter and spliced the
    connector to my old adapter (the connector was the broken part on teh
    old one). This worked but the size wasn't correct so the plug would fall
    out of the laptop any time you moved it (or the wind blew). I ran w/
    this for about 2 weeks.

    That is the background. Recently, I ebayed a replacement adapter. I
    plugged it in and it worked fine. Except... shortly after you plug it
    in a slight hissing/squeaking becomes audible. It seems to get louder
    and louder until I, out of fear for the delicate internals, diconnect
    it. The sound is almost certainly electricity arcing, it is very
    reminicent of that experiment from science class where you can see
    elec. arc up the two poles.

    My questions are these:
    1. Is this going to hurt the laptop?
    2. Even if it doesn't hurt it, it is going to drive me insane. How
    can I stop it. I was thinking of maybe some sort of conductive goo?
    3. Is the problem most likely in the plug or the adapter itself. ie.
    Can I splice the new head onto the old adapter?


    Thanx for your time.
    ej
     
  2. Tom Biasi

    Tom Biasi Guest

    Hi,
    From your description I really don't know what is happening. The high
    voltage type arc that you describe is not likely. Probably switching supply
    noise, at any rate I wouldn't use it on a computer.
    Tom
     
  3. carpenoctem

    carpenoctem Guest

    at any rate I wouldn't use it on a computer.

    Yeah, that's what I figured. I am not seeing the arc but the sound is
    very reminscent of it. it builds up and then "pops" and then starts
    from the lowest again. at least once or twice a second.

    do you think this would more likely be a problem w/ the connector that
    plugs into the computer or hte power adapter itself? The sound is
    definitely from the connector.

    thanx for your time
    ej
     
  4. Gerry Cohn

    Gerry Cohn Guest

    Hi,
    I have had to service several Acer machines because they use a really crappy
    PCB mounted
    connector for the power inlet. I have found that the soldering of this
    connector to the board is
    often very poor. In three of the last four Acers that I have looked at I
    found dry solder joints on
    this connector. Every one of these machines had the same 'hissing' sound
    that yoy refer to.
    The problem appears to be tarnished pins on the connector not soldering
    properly
    when the boards go over the wave. It looks like Acer have used batch of
    ancient surplus stock
    that they have aquired at some stage.
    The problem takes a while to show up, but show up it will, as you have now
    found.
    After working on these machines for a while, I have permanently sworn off
    Acer.
    The build quality is questionable to say the least.

    Your best bet, if you are confortable doing so, is to open up the machine
    and extract the main board.
    You will find a plastic guard sheet in the top right corner of the machine
    under the area where the power
    inlet connector is located. This sheet is attached with double adhesive and
    will have to be gently peeled
    back in order to re-solder the connector, Make sure you use solder with a
    very active flux to overcone the
    tarnish on the pins. After soldering, gently rock the connector from side to
    side. If it is properly soldered it should
    not move. If the solder joint is dry you will notice the terminal on the
    side of the connector moving in the PCB.

    HTH
    Gerry

    ** The ultimate oxymoron - An Honest Politician! **
     
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