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comp mainboard repair

Discussion in 'Electronic Repair' started by [email protected], Apr 8, 2007.

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  1. Guest

    I just recieved a cpu and mainboard after upgrading a friends
    computer.
    Upon inspection of my "new" board, I noticed many of the electrolytic
    caps on the board were bloated and leaking. Just for fun, I salvaged
    some caps from a few junk boards I had, and replaced all but 3
    caps(didnt have that value). There are no additional specs on the caps
    other than a temp rating(105C). Any suggestions? or are generic
    aluminum electrolytics of the proper value (2200Uf 16V) suitable?
     
  2. CJT

    CJT Guest

    Use good grade 2200 uF, 16V, 105C of the same physical dimensions.

    I usually get mine from Digikey, but there are many other vendors.

    There's nothing special about the caps on motherboards (unless you
    consider the 105C spec "special").
     
  3. Eeyore

    Eeyore Guest

    They usually need to be 'low ESR' types suitable for high frequencies but seeing
    as you got the replacements from other mobos, that should be just fine. 105C
    rating simply lasts longer in this kind of use than the more common 85C parts.

    Graham
     
  4. James Sweet

    James Sweet Guest


    Ideally you want low ESR caps of the same or slightly greater voltage
    and temp rating. You can't go too high in most cases or they won't
    physically fit in the space. I fixed a pile of boards with this problem
    a few years ago, there was a huge rash of faulty capacitors.
     
  5. www.badcaps.net has lots of info, and you can't just use any 105C caps
    but need those with low ESR. DigiKey.com, Mouser.com are some good
    sources, but I hope that you don't need any that are 8mm diameter
    because they can be hard to find in larger values.
     
  6. Are you sure? Because I thought that the switching regulators on
    mobos required low-ESR caps, not just any 105C caps, and that was why
    different model caps were used for the regulator than for bypass, even
    when all the caps were of the same brand. Also I've seen many mobos
    with high quality caps in the regulator circuitry, almost always
    Japanese brands, but lower quality Taiwanese or Chinese caps for
    bypass, and this included budget brand mobos, like Asrock and ECS
    (but not ECS' own budget brand, PCchips).
     
  7. Franc Zabkar

    Franc Zabkar Guest

    I don't know what the relationship is like today, but soon after their
    merger, PCChips and ECS sold exactly the same boards under different
    model names.

    - Franc Zabkar
     
  8. Franc Zabkar

    Franc Zabkar Guest

  9. My ECS K7VTA3 v. 8 was identical to a PCChips mobo, except the latter
    was red, lacked one set of jumper pins, and had soldered jumper wires
    in place of fuses. And with another design, the ECS version had
    Chemicon capacitors for the CPU voltage regulator but OST caps
    everywhere else, while the PCChips version had OST everywhere. IOW
    PCChips is cheap ECS' even cheaper line of mobos. :(

    I'm taking back an ECS P4M800Pro-M mobo made for the Intel Core2 CPU
    because it doesn't have STR (suspend to RAM). I can't believe that a
    mobo so new would lack STR.
     
  10. Franc Zabkar wrote:

    I have a Soyo retail mobo based on the intel 810i chipset, and it has
    Taiwan brand
    capacitors all over it, but the same mobo used by Gateway uses only
    higher quality
    Japanese caps, including Sanyo OS-CONs.
     
  11. Franc Zabkar

    Franc Zabkar Guest

    FWIW, OST do make solid caps:
    http://www.ost.com.tw/PDF/SC/SC_OST_PUS.pdf

    Whether PCChips uses them is another matter, though.

    While I was on the OST web site, I noticed that the expected lifetimes
    for capacitors when operated at their rated temperature are
    surprisingly low:

    http://www.ost.com.tw/products_ec_list.asp

    - Franc Zabkar
     
  12. Dave Garland

    Dave Garland Guest

    I thought they were all flushed from the pipeline by now, but recently
    I've seen bad ASROCK K7S41GX boards purchased about 2 years ago going
    bad (one of them on my own computer, but I had sold several others and
    now they're all going bad). Arrgh.

    Dave
     
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