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Thread: Help with pigtail mod

  1. #1
    Just burned his ISO Dohnuts's Avatar
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    Default Help with pigtail mod

    Hi

    I found an old USB wifi adaptor laying about the office and noticed that it is well supported in BT. I also had an old RPSMA pigtail laying around and decided to marry to the two.

    This where it started going wrong :-(

    Here a picture of the board:

    hxxp://g.imagehost.org/view/0377/Wifi-adaptor

    I removed the internal antenna from the board but in doing so I also damaged the board (marked A). The ground was connected to point B.

    I was wondering if anyone can point out another place on the board where I can solder the pigtail.

  2. #2
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    It doesn't really look like you can solder the pigtail anywhere else on the board. BTW what is the wifi adapter you are doing this mod too? I found that when doing this particular mod it was pretty easy with the Linksys WUSB54G V4 adapter. But, there are some problems with that adapter.

    You don't plan on trying to solder the pigtail anywhere else on that same board do you? It looks like you got some pretty bad heat damage on the one you got there.

  3. #3
    My life is this forum Barry's Avatar
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    You might be able to make it work by cutting the line between c35 and the "big" white box, then soldering to the line between your cut and c35. Ground will still be the old ground point, or I think you could solder to the shielding around the radio circuits. You'll lose the diversity circuit, but with a better antenna it won't matter.
    Of course, if you really wanted to have some fun, go to Wal-Mart late at night and ask the greeter if they could help you find trashbags, roll of carpet, rope, quicklime, clorox and a shovel. See if they give you any strange looks. --Streaker69

  4. #4
    Just burned his ISO Dohnuts's Avatar
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    Hi Laffing man

    The board is from a "Cable & Wireless" 802.11g adaptor. Model no: CWUSBAMIMO(2006/05) based around the RA2573 chipset. Funnily enough it still works ok using the diversity antenna on the circuit board, though I might splice into that somewhere and solder in a pigtail.

    It's basically a throw away item, I have about a dozen other USB adaptors that I've successfully modified, my favourite being the 3COM 3CRUSB10075 which uses a Zydas 1211 chipset - this is the most sensitive adaptor I've ever used, it picks up and injects to AP's that other adaptors just can't reach.

  5. #5
    Senior Member Thorn's Avatar
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    Tracing the circuit, it looks like there is an internal antenna on the other side of the board.
    Thorn
    Stop the TSA now! Boycott the airlines.

  6. #6
    Just burned his ISO Dohnuts's Avatar
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    Barry

    Just so we're both on the same page, I've taken another picture and marked it up:

    hxxp://f.imagehost.org/0329/CutCutCut.jpg

    Are you saying cut at point (C), solder the at point (D) and ground and pont (E)?

    Thorn, you're right! hxxp://f.imagehost.org/0102/086.jpg

  7. #7
    Senior Member Thorn's Avatar
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    Quote Originally Posted by Dohnuts View Post
    Thorn, you're right! hxxp://f.imagehost.org/0102/086.jpg
    Of course I'm right. (No modesty here!)

    If you solder an external pigtail to the bare copper at the point D6 (D8?) on the upper left, it should work. That's the internal antenna. You can attach the shield to the via down and to the right of that.
    Thorn
    Stop the TSA now! Boycott the airlines.

  8. #8
    Just burned his ISO Dohnuts's Avatar
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    OK, so I finally got this adaptor modded.

    I carefully removed the diversity chip with a pair of small snips and some tweezers. After a little clean up I was left with this:

    hxxp://f.imagehost.org/0155/RemovedDiversityChip.jpg

    I soldered to the pin and grounded to another area of the board. On a side note getting the solder to stick to the pin was trivial, soldering to the actual circuit board was a nightmare and took about 10 attempts. I immediately hot glued everything to captivate the pigtail:

    hxxp://f.imagehost.org/0461/Board-complete.jpg

    A little persuasion to the case and here's the finished adaptor:

    hxxp://f.imagehost.org/0147/complete.jpg

    I'm going to give this adaptor a 7/10 for BT usage - receive sensitivity is good and injection is also very effective.

    It gets a 2/10 for modifiability - there's something weird about the resin on the circuit board that makes it a real pain to solder/de-solder and do clean up work.

  9. #9
    Just burned his ISO Dohnuts's Avatar
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    And in case anyone is interested here's how it fits in with the other adaptors we have in the office.

    Taking in to account receive sensitivity, injection ability, power drain etc.

    hxxp://f.imagehost.org/0847/Adaptors.jpg

  10. #10
    Just burned his ISO
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    hello dohnuts,

    i also have the 3com usb adaptor,dont know much about electronics but know how to solder.
    i would like to mod the adapter.and afterwards build a external anntenna.

    can you please help me out?

    hello,

    i have the 3com 3CRUSB10075 usb adaptor,dont know much about electronics but know how to solder.
    i would like to mod the adapter.and afterwards build a external anntenna.

    can you please help me out?

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