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3 blown Power supply's in 6 months.



 
 
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  #46  
Old May 9th 05, 07:29 PM
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"w_tom" wrote in message
...
First thing that power supply must provide is a long
list of written and numeric specs.


This is still a user beware situation. Many PSU makers actually lie
about what load their product will support. They may rate the PSU as a
400W unit but include the voltages and their supposed load support when
those voltages aren't used, or they list an aggregate load for a common
rail voltage when the combined or simultaneously load will be much
smaller. That 400W cheapie PSU may only be able to actually support a
concurrent 200W to 300W load. Figure 50% to 75% of actual wattage
rating from a cheapie PSU. So you may simply be trying to suck out 300W
of an actual load from a PSU that can only supply 200W but has a "400W"
sticker on it. A good PSU will tell you what is the load available per
tap but also mention if there are any caveats regarding a combined load
limit across taps.

Just because it says 400W on its sticker doesn't mean it will actually
support that load level on all its taps at the same time. Not only is
that a concern but also many cheapie PSU makers will outright lie about
what load can be safely applied to any tap. There is also the problem
of excessive ripple. Although many computer components are designed to
accommodate some ripple, they won't handle it when it is so severe as to
look like a sawtooth pattern on an oscilloscope. It sounds like the OP
has been trying to get by on cheap PSUs and then wondering why they
blow. Sort of like buying the cheapest tires and expecting them to be
equivalent to the pricey ones. Your PSU provides the lifeblood of your
computer.

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  #47  
Old May 9th 05, 07:29 PM
external usenet poster
 
Posts: n/a
Default

"w_tom" wrote in message
...
First thing that power supply must provide is a long
list of written and numeric specs.


This is still a user beware situation. Many PSU makers actually lie
about what load their product will support. They may rate the PSU as a
400W unit but include the voltages and their supposed load support when
those voltages aren't used, or they list an aggregate load for a common
rail voltage when the combined or simultaneously load will be much
smaller. That 400W cheapie PSU may only be able to actually support a
concurrent 200W to 300W load. Figure 50% to 75% of actual wattage
rating from a cheapie PSU. So you may simply be trying to suck out 300W
of an actual load from a PSU that can only supply 200W but has a "400W"
sticker on it. A good PSU will tell you what is the load available per
tap but also mention if there are any caveats regarding a combined load
limit across taps.

Just because it says 400W on its sticker doesn't mean it will actually
support that load level on all its taps at the same time. Not only is
that a concern but also many cheapie PSU makers will outright lie about
what load can be safely applied to any tap. There is also the problem
of excessive ripple. Although many computer components are designed to
accommodate some ripple, they won't handle it when it is so severe as to
look like a sawtooth pattern on an oscilloscope. It sounds like the OP
has been trying to get by on cheap PSUs and then wondering why they
blow. Sort of like buying the cheapest tires and expecting them to be
equivalent to the pricey ones. Your PSU provides the lifeblood of your
computer.

  #48  
Old May 9th 05, 07:32 PM
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Posts: n/a
Default

"J-Dee" wrote in message
...
im from UK and every power cable has to have a fuse in UK so suppose
it
depends where your from. if you use fuses it could well be a problem.



If that is true then the fuse needs to be the slow-blow type. The
sudden burst of amps surging through a normal fuse could easily blow it
when the computer is powered on. The slow-blow fuse will prevent it
from opening for a short one-time surge. However, if the fuse in the
power cord blew then the OP would be asking why he has to keep replacing
power cords or the fuses in them. He is saying that he is replacing
PSUs. Even if he replaced the PSU, it wouldn't work until he replaced
the power cord fuse, so he would've still mentioned having to replace
fuses. Doesn't sound like it is a fuse problem.

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  #49  
Old May 9th 05, 07:32 PM
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"J-Dee" wrote in message
...
im from UK and every power cable has to have a fuse in UK so suppose
it
depends where your from. if you use fuses it could well be a problem.



If that is true then the fuse needs to be the slow-blow type. The
sudden burst of amps surging through a normal fuse could easily blow it
when the computer is powered on. The slow-blow fuse will prevent it
from opening for a short one-time surge. However, if the fuse in the
power cord blew then the OP would be asking why he has to keep replacing
power cords or the fuses in them. He is saying that he is replacing
PSUs. Even if he replaced the PSU, it wouldn't work until he replaced
the power cord fuse, so he would've still mentioned having to replace
fuses. Doesn't sound like it is a fuse problem.

--
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For e-mail Reply: remove "DELETE", add "~VN56~" to Subject.
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  #50  
Old May 9th 05, 07:34 PM
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Posts: n/a
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"RobW" wrote in message
...
I pulled the case and found a fuse that now resembles a used
firecracker which I guess came out of the PSU. (the PSU has a bottom
intake fan with large gaps).
I am going to take Leythos's suggestion and investigate which fuse on
the PSU is blown. I may have to get someone who knows what they are
looking at to examine it, :-).
I am in Australia and the mains is 240VAC.
The power leads have no fuses.
Thanks again and I will post the outcome for anyone who is interested.



That fuse usually means you are drawing too many amps from the PSU. You
are overheating and overloading the PSU. See my other post regarding
the use of cheapie power supplies and why you cannot simply rely on the
stickered wattage rating. It also shows that you are using cheapie
PSUs. The better ones use a reset circuit that will reset after awhile
(when the heat dissipates). A fuse is cheaper.

--
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  #51  
Old May 9th 05, 07:34 PM
external usenet poster
 
Posts: n/a
Default

"RobW" wrote in message
...
I pulled the case and found a fuse that now resembles a used
firecracker which I guess came out of the PSU. (the PSU has a bottom
intake fan with large gaps).
I am going to take Leythos's suggestion and investigate which fuse on
the PSU is blown. I may have to get someone who knows what they are
looking at to examine it, :-).
I am in Australia and the mains is 240VAC.
The power leads have no fuses.
Thanks again and I will post the outcome for anyone who is interested.



That fuse usually means you are drawing too many amps from the PSU. You
are overheating and overloading the PSU. See my other post regarding
the use of cheapie power supplies and why you cannot simply rely on the
stickered wattage rating. It also shows that you are using cheapie
PSUs. The better ones use a reset circuit that will reset after awhile
(when the heat dissipates). A fuse is cheaper.

--
__________________________________________________ __________
** Post your replies to the newsgroup - Share with others **
For e-mail Reply: remove "DELETE", add "~VN56~" to Subject.
__________________________________________________ __________

  #52  
Old May 9th 05, 07:36 PM
Richard Urban
external usenet poster
 
Posts: n/a
Default

Hell. There were times in my past career when I would not even fuse a 10HP
440/460V motor. I would rather have it burn up than have a fuse blow at an
inopportune time. Example: an emergency ventilator in an explosive
atmosphere. When the LFL (lower flammability limit) reached 7.5% that motor
came on and ran until the environment was again safe or the motor destroyed
itself because of "whatever"!

--
Regards,

Richard Urban

aka Crusty (-: Old B@stard :-)

If you knew as much as you think you know,
You would realize that you don't know what you thought you knew!


"Mike Hall (MS-MVP)" wrote in message
...
Tom

A fuse does NOT exist purely to save human life.. the fuses inside a hi-fi
power amplifier or CB or computer power supply are there to protect
circuits.. some will be fast blow, some will be slow blow, and some are
thermal types..

Note also that automotive fuses do NOT exist to save human life.. and if
you had followed any links on the URL given to you, that would have become
patently clear to you too..


--
Mike Hall
MVP - Windows Shell/User
http://dts-l.org/goodpost.htm





"w_tom" wrote in message
...
Why did you provide a URL for circuit protection devices?
Those are not fuses? Did you assume that because it is a
Littelfuse product, then it must be a fuse? Or did you first
review the datasheets before posting? Cited are applications
for circuit protection devices .... which are not fuses.

Circuit protector devices and fuses are not the same
device. You have claims a device called TMOV is a fuse. That
is wrong. Go back and learn about TMOVs ... "available in 14
and 20 mm disc size with and without a monitor lead (to alert
you that the thermal element has opened). The 14 mm parts are
rated to 6kA and the 20 mm parts are rated to 10kA." Do you
claim these "6,000 and 10,000 amp fuses" would stop electronic
damage?

Again, fuses blow after the electronic damage has happened
so that the human is not put at risk. This being basic
electrical knowledge that even a computer assembler should
know.

"Mike Hall (MS-MVP)" wrote:
Take a look at this..
http://www.littelfuse.com/cgi-bin/r....ION=oNm8TFzMb5

Fuses are not just found in domestic, industrial and automotive
power supply lines..





  #53  
Old May 9th 05, 07:36 PM
Richard Urban
external usenet poster
 
Posts: n/a
Default

Hell. There were times in my past career when I would not even fuse a 10HP
440/460V motor. I would rather have it burn up than have a fuse blow at an
inopportune time. Example: an emergency ventilator in an explosive
atmosphere. When the LFL (lower flammability limit) reached 7.5% that motor
came on and ran until the environment was again safe or the motor destroyed
itself because of "whatever"!

--
Regards,

Richard Urban

aka Crusty (-: Old B@stard :-)

If you knew as much as you think you know,
You would realize that you don't know what you thought you knew!


"Mike Hall (MS-MVP)" wrote in message
...
Tom

A fuse does NOT exist purely to save human life.. the fuses inside a hi-fi
power amplifier or CB or computer power supply are there to protect
circuits.. some will be fast blow, some will be slow blow, and some are
thermal types..

Note also that automotive fuses do NOT exist to save human life.. and if
you had followed any links on the URL given to you, that would have become
patently clear to you too..


--
Mike Hall
MVP - Windows Shell/User
http://dts-l.org/goodpost.htm





"w_tom" wrote in message
...
Why did you provide a URL for circuit protection devices?
Those are not fuses? Did you assume that because it is a
Littelfuse product, then it must be a fuse? Or did you first
review the datasheets before posting? Cited are applications
for circuit protection devices .... which are not fuses.

Circuit protector devices and fuses are not the same
device. You have claims a device called TMOV is a fuse. That
is wrong. Go back and learn about TMOVs ... "available in 14
and 20 mm disc size with and without a monitor lead (to alert
you that the thermal element has opened). The 14 mm parts are
rated to 6kA and the 20 mm parts are rated to 10kA." Do you
claim these "6,000 and 10,000 amp fuses" would stop electronic
damage?

Again, fuses blow after the electronic damage has happened
so that the human is not put at risk. This being basic
electrical knowledge that even a computer assembler should
know.

"Mike Hall (MS-MVP)" wrote:
Take a look at this..
http://www.littelfuse.com/cgi-bin/r....ION=oNm8TFzMb5

Fuses are not just found in domestic, industrial and automotive
power supply lines..





  #54  
Old May 9th 05, 07:40 PM
external usenet poster
 
Posts: n/a
Default

"Leythos" wrote in message
...

Most computer PSU's use CAPS on the DC side and they don't have more
than 20+ VDC on most of them, the caps will also discharge in a short
amount of time due to the way a PSU is designed.



It is not so much of getting a small shock, if any. It is usually more
the case of causing physical damage to yourself due to the involuntary
quick withdraw of your hand. Getting a shock often doesn't do much harm
when working on electronics, but you've spent 5 minutes winding your
fingers, hand, and arm in amongst all the cords and components, some of
which have barbs or sharp edges. When you get shocked, you withdraw in
a straight line and drag your skin across all those jaggies. The shock
didn't hurt you. You hurt your because of your reaction the the shock.
The bzzzt or buzz might not hurt, but your hand or arm might look like
you had a fight with a feral cat.

I'd give the PSU about 10 minutes to discharge, and that is WITH the
power cord connected to the computer and to the outlet. If the OP is
sucking out an excessive amount of current, there is also a good chance
that some parts are hot inside.

--
__________________________________________________ __________
** Post your replies to the newsgroup - Share with others **
For e-mail Reply: remove "DELETE", add "~VN56~" to Subject.
__________________________________________________ __________

  #55  
Old May 9th 05, 07:40 PM
external usenet poster
 
Posts: n/a
Default

"Leythos" wrote in message
...

Most computer PSU's use CAPS on the DC side and they don't have more
than 20+ VDC on most of them, the caps will also discharge in a short
amount of time due to the way a PSU is designed.



It is not so much of getting a small shock, if any. It is usually more
the case of causing physical damage to yourself due to the involuntary
quick withdraw of your hand. Getting a shock often doesn't do much harm
when working on electronics, but you've spent 5 minutes winding your
fingers, hand, and arm in amongst all the cords and components, some of
which have barbs or sharp edges. When you get shocked, you withdraw in
a straight line and drag your skin across all those jaggies. The shock
didn't hurt you. You hurt your because of your reaction the the shock.
The bzzzt or buzz might not hurt, but your hand or arm might look like
you had a fight with a feral cat.

I'd give the PSU about 10 minutes to discharge, and that is WITH the
power cord connected to the computer and to the outlet. If the OP is
sucking out an excessive amount of current, there is also a good chance
that some parts are hot inside.

--
__________________________________________________ __________
** Post your replies to the newsgroup - Share with others **
For e-mail Reply: remove "DELETE", add "~VN56~" to Subject.
__________________________________________________ __________

  #56  
Old May 9th 05, 07:40 PM
Leythos
external usenet poster
 
Posts: n/a
Default

In article , Vanguard says...
"J-Dee" wrote in message
...
im from UK and every power cable has to have a fuse in UK so suppose
it
depends where your from. if you use fuses it could well be a problem.



If that is true then the fuse needs to be the slow-blow type. The
sudden burst of amps surging through a normal fuse could easily blow it
when the computer is powered on. The slow-blow fuse will prevent it
from opening for a short one-time surge. However, if the fuse in the
power cord blew then the OP would be asking why he has to keep replacing
power cords or the fuses in them. He is saying that he is replacing
PSUs. Even if he replaced the PSU, it wouldn't work until he replaced
the power cord fuse, so he would've still mentioned having to replace
fuses. Doesn't sound like it is a fuse problem.


Actually the OP stated, later, that he found a fuse blown inside the PSU
once he opened it.

--
--

remove 999 in order to email me
  #57  
Old May 9th 05, 07:40 PM
Leythos
external usenet poster
 
Posts: n/a
Default

In article , Vanguard says...
"J-Dee" wrote in message
...
im from UK and every power cable has to have a fuse in UK so suppose
it
depends where your from. if you use fuses it could well be a problem.



If that is true then the fuse needs to be the slow-blow type. The
sudden burst of amps surging through a normal fuse could easily blow it
when the computer is powered on. The slow-blow fuse will prevent it
from opening for a short one-time surge. However, if the fuse in the
power cord blew then the OP would be asking why he has to keep replacing
power cords or the fuses in them. He is saying that he is replacing
PSUs. Even if he replaced the PSU, it wouldn't work until he replaced
the power cord fuse, so he would've still mentioned having to replace
fuses. Doesn't sound like it is a fuse problem.


Actually the OP stated, later, that he found a fuse blown inside the PSU
once he opened it.

--
--

remove 999 in order to email me
  #60  
Old May 9th 05, 07:49 PM
Richard Urban
external usenet poster
 
Posts: n/a
Default

An old horse story!

I was doing T.V. repair in the 60's. There was a new high rise in Fort Lee,
NJ. One of our technicians was up on the 9th floor working on a woman's
console T.V. (friggin HUGE). He was squatting down behind the set - the
power was off. He accidentally touched the 2nd anode on the CRT. His legs
convulsed and sprung him backward, through the open sliding balcony doors
and over the rail to his death!

He was my friend.

--
Regards,

Richard Urban

aka Crusty (-: Old B@stard :-)

If you knew as much as you think you know,
You would realize that you don't know what you thought you knew!


Vanguard wrote in message ...
"Leythos" wrote in message
...

Most computer PSU's use CAPS on the DC side and they don't have more
than 20+ VDC on most of them, the caps will also discharge in a short
amount of time due to the way a PSU is designed.



It is not so much of getting a small shock, if any. It is usually more
the case of causing physical damage to yourself due to the involuntary
quick withdraw of your hand. Getting a shock often doesn't do much harm
when working on electronics, but you've spent 5 minutes winding your
fingers, hand, and arm in amongst all the cords and components, some of
which have barbs or sharp edges. When you get shocked, you withdraw in a
straight line and drag your skin across all those jaggies. The shock
didn't hurt you. You hurt your because of your reaction the the shock.
The bzzzt or buzz might not hurt, but your hand or arm might look like you
had a fight with a feral cat.

I'd give the PSU about 10 minutes to discharge, and that is WITH the power
cord connected to the computer and to the outlet. If the OP is sucking
out an excessive amount of current, there is also a good chance that some
parts are hot inside.

--
__________________________________________________ __________
** Post your replies to the newsgroup - Share with others **
For e-mail Reply: remove "DELETE", add "~VN56~" to Subject.
__________________________________________________ __________



 




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