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Motherboard fuses - missing?

Discussion in 'Electronic Basics' started by larry moe 'n curly, Aug 17, 2005.

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  1. I have an Asrock (budget Asus) K7VT4A Pro ATX motherboard with three
    empty spaces where it seems that fuses would normally go.

    They're all at the rear, near the I/O ports. At locations F1 and F2 I
    measure 5V across their solder pads, while at location F2 I measure 0V
    between them (each solder pad is at 4.8V).

    I've seen resettable fuses installed in locations like this on some
    other motherboards, and I've even seen some with soldered jumpers.

    What's going on here?
     
  2. Tom Biasi

    Tom Biasi Guest

    Mobos often have empty spaces where it looks like something could go. Not
    every model uses every space.
    RTFM: http://www.asrock.com.tw/Drivers/Manual/K7VT4APro_um.pdf :)
     
  3. I have RTFM, but TFM doesn't mention the fuse, and I doubt that these
    missing fuses are for any missing functions. I've also never heard of
    TFM ever going into this much detail about the hardware.
     
  4. Tom Biasi

    Tom Biasi Guest

    If they are not there you probably don't need them.
     
  5. Yes, but why specifically is the circuit board laid out for those
    fuses?
     
  6. kony

    kony Guest

    It's easier to make one board design that's a jack of all
    trades, then later modify it only the (least) amount
    necessary to meet some requirement or cut cost or (whatever
    the scenario). Did you determine how the (typically fused)
    ports are getting power since those fuse positions are
    unfilled?
     
  7. Because it's cheaper to make one board, and then stuff it as needed,
    than have to make a different board for every variant, or when a small
    change is necessary.

    Let's say they make 100,000 boards. They start stuffing and run out
    of a specific part at the 10,000 mark. If they can't get the part that
    fits, then they have to scrap the remaining 90,000 boards. But when
    they have foresight, they have designed the board to take some different
    parts sizes just in case.

    Or, and this is common in consumer equipment, one board has some features
    that the other doesn't. So long as it doesn't add too much to the board
    space, it's cheaper to have one board that has all the possibilities than
    multiple boards.

    So the fuses that are "missing" may exist on the board in a different
    form. Or they may be part of feature that isn't part of what you bought,
    so you don't get it.

    Meanwhile, someone else might have the same board, and have those
    fuses in place while fuses in a different package elsewhere are "missing".
    The traces on the board simply put both in parallel so what is available
    can fit the board. Or, they have some extra feature that requires some
    of the "missing" parts, so the space is filled.

    Michael
     
  8. Conor

    Conor Guest

    **** sake...you really have no idea do you?

    It is far cheaper for manufacturers to design and stock one PCB to work
    across many models than to design and make a PCB for each individual
    model.


    --
    Conor

    If Pac-Man affected us as kids, we'd all be running around in darkened
    rooms, munching magic pills and listening to repetitive electronic
    music.
     
  9. I realize that, but in this case I can't imagine why the manufacture
    would vary the design because the fuses are for keyboard (and maybe
    mouse), USB, and Ethernet, and this particular mobo doesn't seem to
    have any missing features for these because it does allow wake on
    keyboard/mouse/USB/Ethernet.
     
  10. Conor

    Conor Guest

    For that particular model.


    --
    Conor

    If Pac-Man affected us as kids, we'd all be running around in darkened
    rooms, munching magic pills and listening to repetitive electronic
    music.
     
  11. kony

    kony Guest


    Yes, BUT for that particular model the fuses ARE missing.
    Our presumptions about why they might have the fuse spots
    still doesn't address his original query.
     
  12. Ken Weitzel

    Ken Weitzel Guest

    Hi...

    Just thinking out loud... not only different models, but
    that one board design will have been designed for use in
    different parts of the world.

    Perhaps outher countries have different code requirements for
    things "extended from" the main chassis?

    Wouldn't explain a missing fuse all by itself, but perhaps
    one jumper is eliminated elsewhere and then the fuse is
    required...

    Just a thought.

    Ken
     
  13. kony

    kony Guest

    It's an interesting thought but the remaining question is
    still, if the fuse isn't installed _and_ the fuse location
    isn't jumpered, why and where did they reroute the power for
    the ports? "Usually" when a fuse is (or isn't) used, the
    power is still delivered on same traces either way, the
    circuit change is prior to that point.
     
  14. That makes sense.

    This is the first time I've seen a mobo made for fuses where the
    left-out fuses weren't substituted with jumper wires (PC Chips, some
    ECS) or copper traces between each fuse location's solder pads.
     
  15. Curly Howard

    Curly Howard Guest

    I can't tell you why, or how. But a suggestion might help.

    I've been doing PC Repair for a long time. And I've often seen the same
    mobo design used by different manufacturers. And in the same
    manufacturer, I've seen boards that are the same layout, but different in
    the number of components, the one with less components on the board being
    the cheaper version.

    What I would try to do is find other boards on the manufacturers website
    with the same layout. Often they include a picture of the board (not
    always the best rez) that might show you what you're looking for.

    I've often seen boards that are the same layout from Chaintech, PC Chips,
    Asus, Epox and others. It's a pain in the tukas, but you might also be
    able to find a board with the same layout but different features with one
    of these other vendors.

    The boards will always be the same size physically, and have the same
    locations of the CPU socket and primary chipset(s). But they may have a
    different number of bus interfaces, or memory sockets. And often they
    have different bioses. However, I have (in the past) been able to use
    one vendor's drivers to make a piece of hardware work.

    Hope that helps lmac. :)

    Curly

    yak, yak, yak, oooooohh....
     
  16. Conor

    Conor Guest

    Because its a pointless one. I could rabbit on incessantly about
    buffers etc but what's the point?


    --
    Conor

    If Pac-Man affected us as kids, we'd all be running around in darkened
    rooms, munching magic pills and listening to repetitive electronic
    music.
     
  17. kony

    kony Guest

    And, the ports DO work. It was not a matter of omitting
    fuses or jumpers for features not present if these are as
    described. So, you have to have an alternate way of getting
    the power to those ports if it's not traveling the same path
    as (practically any) motherboard out there. Perhaps if
    you'd more carefully examined more boards you'd appreciate
    the distinction, as larry moe 'n curly did have a valid
    point and had also recognized that when the fuses aren't
    employed there IS a jumper in it's place or copper track
    across the pads. This particular board he has is unique in
    this respect.

    The point is that some of us are interested in motherboard
    layout/design/etc... it is a hardware group.
     
  18. Franc Zabkar

    Franc Zabkar Guest

    What is it about the OP's post that you don't understand? He has
    stated that all the motherboard's IO functions are operational. This
    means that *all* devices are getting their power from the motherboard,
    despite several fuse locations being unpopulated, ie *open*. So the
    OP's question as to what function these missing fuses would have
    performed is a valid and logical one.


    - Franc Zabkar
     
  19. Franc Zabkar

    Franc Zabkar Guest

    What is it about the OP's post that you don't understand? He has
    stated that all the motherboard's IO functions are operational. This
    means that *all* devices are getting their power from the motherboard,
    despite several fuse locations being unpopulated, ie *open*. So the
    OP's question as to what function these missing fuses would have
    performed is a valid and logical one.


    - Franc Zabkar
     
  20. In this case, maybe a certain country has different safety standards
    that require the keyboard, mouse, etc. to be fused, so on the models
    sent to that country they are fused, and the same model marketed in
    other countries leaves the fuse out and maybe puts a cheaper jumper in
    to save money on components.
    In large quantities the fuse may cost a penny and a jumper may cost 1/10
    of a penny. Over hundreds of thousands of boards it makes a difference.
     
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