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

 
 
Bill
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      31st Jan 2004
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
 
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Snp
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      31st Jan 2004
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.!

--





Snp

Cut THE CRAP To Reply



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"Bill" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> 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



 
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user@domain.invalid
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Posts: n/a
 
      31st Jan 2004


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 Snp 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.

 
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w_tom
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      31st Jan 2004
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
> -------------------------------

 
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do_not_spam_me
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      31st Jan 2004
(E-Mail Removed) (Bill) wrote in message news:<(E-Mail Removed)>...

> 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.
 
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Bill
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      1st Feb 2004
(E-Mail Removed) (do_not_spam_me) wrote in message news:<(E-Mail Removed)>...
> (E-Mail Removed) (Bill) wrote in message news:<(E-Mail Removed)>...
>
> > 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
 
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w_tom
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Posts: n/a
 
      1st Feb 2004
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?

 
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larrymoencurly
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      1st Feb 2004
(E-Mail Removed) (Bill) wrote in message news:<(E-Mail Removed)>...

>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.
 
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