Blown my 400 Watts ATX PS, What's the replacement fuse rating I should use?

Discussion in 'DIY PC' started by Bill, Jan 31, 2004.

  1. Bill

    Bill Guest

    I just blown my 400 Watts ATX power supply fuse by mistakenly
    connecting the floppy power wire to case fan power connector on my
    motherboard (it's a long story why I did that).

    Anyway I opened up the power supply case and try to look and see what
    fuse rating is on the blown fuse but the markings on it is facing the
    circuit board so I can't see it clearly (and I don't have a soldering
    iron at the moment).
    I'm thinking about running out to Radio Shack and get a replacement
    fuse for it.

    Since I'm not too electronic savvy. Can anyone be kind enough to tell
    me what type of fuse and rating I should get? I just wanna make sure I
    put an identical one in there.

    Here's what's on the lable of the ATX power supply.

    CYBERZONE, Model: KC-400
    -------------------------------
    Input: 115V/230V AC 60/50Hz
    10A/5A
    Output: 400W MAX
    +5V 25A +3.3V 20A
    +12V 15A -12V 1A
    +5VSB 2A -5A 1A
    -------------------------------

    Thanks
    Bill
     
    Bill, Jan 31, 2004
    #1
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  2. Bill

    Snøøp¥ Guest

    Hi,

    If the fuse has blown inside your PSU, I would seriously consider getting a
    new PSU, as there seems to be a problem with it, especially with it blowing
    the internal fuse,
    if you put the wrong size fuse in, you might/will blow your motherboard, and
    all hardware attached.!

    --





    Snøøp¥

    Cut ¬THE CRAP¬ To Reply



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    "Bill" <> wrote in message
    news:...
    > I just blown my 400 Watts ATX power supply fuse by mistakenly
    > connecting the floppy power wire to case fan power connector on my
    > motherboard (it's a long story why I did that).
    >
    > Anyway I opened up the power supply case and try to look and see what
    > fuse rating is on the blown fuse but the markings on it is facing the
    > circuit board so I can't see it clearly (and I don't have a soldering
    > iron at the moment).
    > I'm thinking about running out to Radio Shack and get a replacement
    > fuse for it.
    >
    > Since I'm not too electronic savvy. Can anyone be kind enough to tell
    > me what type of fuse and rating I should get? I just wanna make sure I
    > put an identical one in there.
    >
    > Here's what's on the lable of the ATX power supply.
    >
    > CYBERZONE, Model: KC-400
    > -------------------------------
    > Input: 115V/230V AC 60/50Hz
    > 10A/5A
    > Output: 400W MAX
    > +5V 25A +3.3V 20A
    > +12V 15A -12V 1A
    > +5VSB 2A -5A 1A
    > -------------------------------
    >
    > Thanks
    > Bill
     
    Snøøp¥, Jan 31, 2004
    #2
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  3. Bill

    Guest

    Re: Blown my 400 Watts ATX PS, What's the replacement fuse ratingI should use?

    Bill wrote:

    > I just blown my 400 Watts ATX power supply fuse by mistakenly
    > connecting the floppy power wire to case fan power connector on my
    > motherboard (it's a long story why I did that).
    >
    > Anyway I opened up the power supply case and try to look and see what
    > fuse rating is on the blown fuse but the markings on it is facing the
    > circuit board so I can't see it clearly (and I don't have a soldering
    > iron at the moment).
    > I'm thinking about running out to Radio Shack and get a replacement
    > fuse for it.
    >
    > Since I'm not too electronic savvy. Can anyone be kind enough to tell
    > me what type of fuse and rating I should get? I just wanna make sure I
    > put an identical one in there.
    >
    > Here's what's on the lable of the ATX power supply.
    >
    > CYBERZONE, Model: KC-400
    > -------------------------------
    > Input: 115V/230V AC 60/50Hz
    > 10A/5A
    > Output: 400W MAX
    > +5V 25A +3.3V 20A
    > +12V 15A -12V 1A
    > +5VSB 2A -5A 1A
    > -------------------------------
    >
    > Thanks
    > Bill


    Remove your blown fuse and take it with you when you go to Radio Shack.
    Even the "Technicians" at RS should be able to tell you what type of
    fuse you need. If they can't, just ask one of their customers. Chances
    are they will know!!!

    As for potentially subjecting your MB to a damaging voltage after the
    fuse replacement as Snøøp¥ suggested, jumper your PS BEFORE you attach
    it and measure the voltages if you can. That is one way to avoid such a
    problem. (His comment is a worthy one, but so is the testing before
    attachment to the MB) If you do not know how to jumper the PS in order
    to make it turn on without a MB attached, do a search. There are plenty
    of articles on how to do this. A fuse costs a lot less than a new PS
    and although there are no guarantees that it will solve your problem, it
    is worth a try.
     
    , Jan 31, 2004
    #3
  4. Bill

    w_tom Guest

    Re: Blown my 400 Watts ATX PS, What's the replacement fuse rating Ishould use?

    All DC outputs on any acceptable power supply can be shorted
    together and not even blow a fuse. Therefore your 400 watt
    power supply is probably missing other essential functions
    because it cannot even conform to a 30+ year defacto
    standard. Intel ATX specs even say how big a shorting wire
    must be and not have any damage. Your damage was from a
    trivial short suggesting your power supply was sold only on
    price; not on value. Therefore, best get a new supply that
    will also include those other important functions.

    For example, what happens if the power supply loses
    regulation? Voltage skyrockets? Does it then destroy other
    computer components? Many supplies bought only on price will
    destroy motherboard, Ram, disk drive, etc because a classic
    'bean counter' mentality resulted in another missing (and
    essential) function. Your fuse probably blew because a power
    supply is defective by design.

    How to select an acceptable power supply? Discussion at
    alt.comp.hardware.pc-homebuilt entitled "GOOD powersupply for
    under $40?" starting 20 Jan 2004, or http://tinyurl.com/3h6wa
    ..

    Bill wrote:
    > I just blown my 400 Watts ATX power supply fuse by mistakenly
    > connecting the floppy power wire to case fan power connector on my
    > motherboard (it's a long story why I did that).
    >
    > Anyway I opened up the power supply case and try to look and see what
    > fuse rating is on the blown fuse but the markings on it is facing the
    > circuit board so I can't see it clearly (and I don't have a soldering
    > iron at the moment).
    > I'm thinking about running out to Radio Shack and get a replacement
    > fuse for it.
    >
    > Since I'm not too electronic savvy. Can anyone be kind enough to tell
    > me what type of fuse and rating I should get? I just wanna make sure I
    > put an identical one in there.
    >
    > Here's what's on the lable of the ATX power supply.
    >
    > CYBERZONE, Model: KC-400
    > -------------------------------
    > Input: 115V/230V AC 60/50Hz
    > 10A/5A
    > Output: 400W MAX
    > +5V 25A +3.3V 20A
    > +12V 15A -12V 1A
    > +5VSB 2A -5A 1A
    > -------------------------------
     
    w_tom, Jan 31, 2004
    #4
  5. (Bill) wrote in message news:<>...

    > I just blown my 400 Watts ATX power supply fuse


    > I opened up the power supply case and try to look and see what
    > fuse rating is on the blown fuse but the markings on it is
    > facing the circuit board so I can't see it clearly


    You could check another 400W power supply's label or calculate the
    amps:

    Unplug the AC cord before opening the power supply because there's
    high voltage everywhere in there, sometimes even on a heatsink. Never
    operate the supply without the cover installed and screwed in place.

    ATX power supplies are approximately 2/3 efficient, meaning one that
    can put out 400W will consume 400W/(2/3) that much, or 600W. Amps =
    watts/volts, or in this case 600W/120V = 5A (or 2.5A if your household
    current is at 240V, as it is in most of Europe). But fuses are
    usually rated for at least 50% more than this, or 7.5A (or 3.75A if
    the AC is at 240V). Fuses are also rated for maximum voltage (250V
    will work, even in the U.S.) and whether they're "quick blow" or "slow
    blow" (when in doubt, choose quick). Most fuses are soldered in
    place and are of the "pig tail" type, but if you don't want to ever
    solder the fuse again, get an inline fuse holder or some circuit board
    fuse clips (if the board is made for them, but watch out for them
    shorting against other tightly packed parts).

    If the new fuse pops almost immediately, very likely you need to
    replace the rectifier diodes or the high voltage transistors, and when
    these transistors are used in a pair, both almost always fail
    together. Most of these transistors need to be electrically insulated
    from their heatsink or they'll short, and the type of insulation
    hardware depends on the packaging, not the part number.
     
    do_not_spam_me, Jan 31, 2004
    #5
  6. Bill

    Bill Guest

    (do_not_spam_me) wrote in message news:<>...
    > (Bill) wrote in message news:<>...
    >
    > > I just blown my 400 Watts ATX power supply fuse

    >
    > > I opened up the power supply case and try to look and see what
    > > fuse rating is on the blown fuse but the markings on it is
    > > facing the circuit board so I can't see it clearly

    >
    > You could check another 400W power supply's label or calculate the
    > amps:
    >
    > Unplug the AC cord before opening the power supply because there's
    > high voltage everywhere in there, sometimes even on a heatsink. Never
    > operate the supply without the cover installed and screwed in place.
    >
    > ATX power supplies are approximately 2/3 efficient, meaning one that
    > can put out 400W will consume 400W/(2/3) that much, or 600W. Amps =
    > watts/volts, or in this case 600W/120V = 5A (or 2.5A if your household
    > current is at 240V, as it is in most of Europe). But fuses are
    > usually rated for at least 50% more than this, or 7.5A (or 3.75A if
    > the AC is at 240V). Fuses are also rated for maximum voltage (250V
    > will work, even in the U.S.) and whether they're "quick blow" or "slow
    > blow" (when in doubt, choose quick). Most fuses are soldered in
    > place and are of the "pig tail" type, but if you don't want to ever
    > solder the fuse again, get an inline fuse holder or some circuit board
    > fuse clips (if the board is made for them, but watch out for them
    > shorting against other tightly packed parts).
    >
    > If the new fuse pops almost immediately, very likely you need to
    > replace the rectifier diodes or the high voltage transistors, and when
    > these transistors are used in a pair, both almost always fail
    > together. Most of these transistors need to be electrically insulated
    > from their heatsink or they'll short, and the type of insulation
    > hardware depends on the packaging, not the part number.



    Thanks for all you guys inputs.

    I actually just got the fuse out after borrowing a soldering iron from
    my friend. It is a pig tail type and it didn't have a fuse holder
    since it's just a cheap generic power supply that came with my cheap
    generic case.

    On the fuse it said F5AL250V, I suppose it's a 5 Amps quick blown type
    fuse.
    I'll try to replace it with an identical one and if it didn't work or
    blow again, I'll probably just save it for parts.

    The power supply had been unpluged for over a day now. Is there still
    chance of getting shock from accidentlly touching the capaicators on
    there to cause any real harm to myself?

    Thanks
    Bill
     
    Bill, Feb 1, 2004
    #6
  7. Bill

    w_tom Guest

    Re: Blown my 400 Watts ATX PS, What's the replacement fuse rating Ishould use?

    Each large capacitor is often discharged in but a minute by
    about a 100k resistor. However in two previous cases, this
    resistor had failed. One without any visual indication. This
    failure is why each cap is first shorted by a screwdriver. If
    cap is not discharges, then you have something else to fix.

    Even more dangerous is the capacitor in microwave ovens. If
    not discharged, that capacitor kills more often.

    I would be very concerned for cherished computer components
    if a shorted power supply was so improperly designed as to
    blow a fuse. Worry because the 'necessary and required' fold
    back current limiting did not work or was missing.

    Bill wrote:
    > Thanks for all you guys inputs.
    > ...
    > The power supply had been unpluged for over a day now. Is there
    > still chance of getting shock from accidentlly touching the
    > capaicators on there to cause any real harm to myself?
     
    w_tom, Feb 1, 2004
    #7
  8. (Bill) wrote in message news:<>...

    >CYBERZONE, Model: KC-400
    >-------------------------------
    >Input: 115V/230V AC 60/50Hz
    > 10A/5A
    >Output: 400W MAX
    >+5V 25A +3.3V 20A
    >+12V 15A -12V 1A
    >+5VSB 2A -5A 1A


    > On the fuse it said F5AL250V, I suppose it's a 5 Amps quick
    > blown type fuse.


    Something is wrong here because:

    (5V x 25A)+(3.3V x 20A)+(12V x 15A)+(12V x 1A)+(5V x 1A)+(5V x 2A) =
    398W.

    With rounding, this seems close enough to 400W, but actually it should
    be a lot higher, except with TruePower type PSUs, including the 500W+
    Fortrons/Sparkles.
    IOW I don't think that this is really a 400W PSU, despite what the
    label says.
    I've seen this before, including with one 400W where the total was
    just 366W.

    > The power supply had been unpluged for over a day now. Is there still
    > chance of getting shock from accidentlly touching the capaicators on
    > there to cause any real harm to myself?


    I have a 6800uF capacitor (about 5-10 times what ATX PSUs use) that I
    charged it to 18V about a year ago, and today it measured 12.64V. But
    I don't think that the capacitors in your PSU will stay up that long
    because the +5V standby part will drain the capacitors in 20 seconds,
    but if it doesn't do the job the 200K or so bleeder resistor across
    each capacitor will drain them in about 20 minutes. But before
    removing the circuit board I'd first measure the voltage across the
    big capacitors, or if I didn't have a meter I'd connect a 10K ohm
    resistor (at least 5 watts) between the case and the heatsink next to
    the big capacitors (this heatsink measured 170VDC during operation
    with Enermax, Antec SmartPower, and Delta PSUs) for 60 seconds. Then
    after removing the circuit board I'd do the same directly across the
    capacitors.
     
    larrymoencurly, Feb 1, 2004
    #8
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