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3Com OfficeConnect recapping

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    3Com OfficeConnect recapping

    For an unrelated project, I bought a cheap 3Com Gigabit OfficeConnect switch ($3). I was expecting some bad caps but ALL of them were toast. Completely toast.

    It had GLORIA and Wendell caps, all of the GLORIA ones were bloated, and some on the verge of releasing electrolyte. Yeah the switch didn't work.

    I did however do a few modifications: I used 470uF 25v instead of 470uF 35v on the two input caps because that's all I had. I tested the voltage and it only went up to 18v. So we're within tolerance.
    I replaced all 330uF 16v with the same 470uF 25v caps. 220uF 16v were replaced with 220uF 10v polymer OSCONs (all that I had on hand). Aaaand, a 47uF I just threw in 100uF. Finally, I added two more 1000uF 6.3v filter caps on two unused pads. I figure they didn't populate those just to cut costs, but I need this thing to run stably, so yeah.

    Here's what it looks like AFTER:


    I tilted the tall 470uF nichicons because I want to ensure they have some clearance. Also regarding the ones that have the weird leg thing going on (near the coil rectifiers), RADIAL capacitors were originally there!
    I've really only seen radials on the old vintage stuff. Oh well. It looks horrible, and I generally hate making imperfect work like that, but I don't feel like hunting down some VXes just for a switch.

    The small blue and small brown caps are ELNA. I have lots of ELNAs kicking around. SILMICs too-- but you wouldn't use a SILMIC on a digital circuit.

    I can see why all of the original cheap capacitors were bloated, this switch gets quite warm after running for a few hours. Running 24/7 and it'll kill those cheap caps in no time (probably why not too many of these are around?)

    Up and operating perfectly (just try to ignore the diskette box):

    #2
    Re: 3Com OfficeConnect recapping

    At first when I saw the photo I thought "Whaaaaat the...???"
    But, if it works!
    If you wanted a neater look you could have probably bent the legs 90 degrees and put them on their sides.

    (By the way, I have 4 diskette boxes like that!)
    Last edited by Agent24; 03-12-2014, 04:46 AM.
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn

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      #3
      Re: 3Com OfficeConnect recapping

      You meant AXIAL capacitors... the ones with leads on each end.

      It's really not a good idea to leave the leads so long but I guess you couldn't do a much better job with a second try, and i wouldn't advise you because you may ruin the pads.

      I also don't like how you soldered the caps but I guess you probably couldn't clear up the holes to push the leads through the boards.

      If it works now, leave it like it is.

      As for "you wouldn't use SILMIC on digital circuits" that's bull. It's still a capacitor. Yeah, I probably wouldn't use it as filtering for a switching power supply but in this circuit, it's probably just some output capacitance on a small linear regulator, so it really won't make a difference that it's an "audio grade" capacitor.

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        #4
        Re: 3Com OfficeConnect recapping

        Even if I desoldered the two axials properly and mounted them in the holes, the length of the leads would basically be the same. So... I thought it would be just easier to do it that way. A better solution would be if 3com didn't use the axials in the first place.

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          #5
          Re: 3Com OfficeConnect recapping

          I like that recap .
          I do mine very similar - usually I have a bunch of quality capacitors but they aren't an exact match for what's in the equipment, so I do some voltage measurements and toss whatever I have plus populating the empty spots. Done many PC motherboards and LCD monitors that way and never had any problems.

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            #6
            Re: 3Com OfficeConnect recapping

            Strange, because another 3com switch I saw before had philips capacitors... good stuff!
            Muh-soggy-knee

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              #7
              Re: 3Com OfficeConnect recapping

              Hello guys i know that´s out of topic, but anyone knows where to download firmware images from old 3com switches? Or someone have of 3com 4200, 4400 and 4500 series? Hp removed all without notice....
              Thanks

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