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Power supply, but no power???



 
 
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  #21  
Old April 12th 05, 12:35 AM
w_tom
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Posts: n/a
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Even in the very first IBM PC, power supply included that
voltage monitoring function (that is now part of the single
IC). A function completely different from the overvoltage
protection circuit - which was also in that IBM PC. Some
power supply controller failures can cause overvoltage.
Totally unacceptable 30 years ago as today. The crowbar (or
equivalent) is required today as it was 30 years ago on switch
mode power supplies. Even the Intel spec (which is only for
switch mode power supplies) says
The overvoltage sense circuitry and reference shall reside
in packages that are separate and distinct from the
regulator control circuitry and reference. No single point
fault shall be able to cause a sustained overvoltage
condition on any or all outputs. The supply shall provide
latch-mode overvoltage protection as defined below.


Nothing new in this requirement. However when dumping
product into a marketplace dominated by 'bean counter'
mentalities, then profits are just too great. How to suspect
a defective power supply? No long list of numerical
specification and no specific listing of overvoltage
protection? Then it is a power supply for the market of 'bean
counting' computer assemblers.

That schematic is further proof that many power supplies are
missing essential functions. Some power supplies fail and
then destroy computer peripherals. A failure directly
traceable to a human who buys on price rather than learn basic
electrical principles. In a market where so many 'experts'
don't even know how how electricity works, then many clone
computers do have $25 power supplies. When a supply fails due
to a manufacturing defect, that 'computer assembler' instead
blames disk drive and motherboard damage on mythical
transients. Why? Most don't even know what electronic part
has failed; let alone know why. Better to just blame
something mythical that others will quickly believe.

Does the power supply provide a long list of numerical
specifications? Many do not provide specs which means
essential overvoltage protection is not required. Its called
dumping. Made profitable by computer assemblers don't even
understand why component manufacturers should provide
numerical specs.

Specs from a responsible power supply manufacturer are quite
long. Abridged election from one responsible power supply
vendor whose supply could never sell for $25 retail - because
it includes essential functions:
Specification compliance: ATX 2.03 & ATX12V v1.1
Short circuit protection on all outputs
Over voltage protection
Over power protection
100% hi-pot test
Efficiency; 100-120VAC and full range: 65%
EMI/RFI compliance: CE, CISPR22 & FCC part 15 class B
Safety compliance: VDE, TUV, D, N, S, Fi, UL, C-UL & CB
Hold up time, full load: 16ms. typical

Does your power supply specifically, with numbers, make
these claims? Why not? Symptoms of a supply that does not
have these essential functions; which can create future
computer failures. Demonstrated are how those with minimal
education recommend and buy power supplies. Schematics from
Franc Zabkar only demonstrate that power supplies without
essential functions are being manufactured. Some computer
failures can be created by power supplies missing these
essential functions. Many computer assemblers may then invent
other suspects to blame. If a power supply failure coincides
with disk drive damage, then first look for a missing
overvoltage protection circuit.

Franc Zabkar wrote:
The chip senses all the rails, including the negative ones, and shuts
down the oscillator if there is a fault condition. No oscillator means
no output. AFAICS, there is no need to crowbar the affected rail(s).
Pins 3,4, and 6 provide the OV functions. Pin 5 is probably equivalent
in function to the OPP (over power protection) pin of the SG6105.
...

Crowbar SCRs/zeners were used in the old days with linear supplies,
but these days most supplies are switchmode. The crowbar would protect
the load from a shorted pass transistor by blowing a fuse, but IMO a
switchmode supply doesn't really need such protection, unless there is
a possibility that the OV sense circuitry itself could fail.
...

The chip's datasheet states that the chip performs under- and
overvoltage sensing/protection, as well as overpower and short circuit
protection. The overpower pin (OPP) requires some inexpensive external
components including a diode and some passives.
...

True, but I suspect Intel is just playing it safe. I have no problem
with a single-chip PSU, especially if the cost savings could be
applied to properly rated parts, particularly the capacitors, diodes,
and magnetics on the DC side.
...

I don't recall seeing any such expensive components in any PC SMPS.
All the PSUs I've seen shut down the PWM controller if there is an OV
condition, but then I've only ever seen generic PSUs. What components
do the more expensive branded PSUs use?

  #22  
Old April 12th 05, 08:02 AM
Franc Zabkar
external usenet poster
 
Posts: n/a
Default

On Mon, 11 Apr 2005 19:35:21 -0400, w_tom put
finger to keyboard and composed:

Even in the very first IBM PC, power supply included that
voltage monitoring function (that is now part of the single
IC). A function completely different from the overvoltage
protection circuit - which was also in that IBM PC. Some
power supply controller failures can cause overvoltage.
Totally unacceptable 30 years ago as today. The crowbar (or
equivalent) is required today as it was 30 years ago on switch
mode power supplies. Even the Intel spec (which is only for
switch mode power supplies) says


The overvoltage sense circuitry and reference shall reside
in packages that are separate and distinct from the
regulator control circuitry and reference. No single point
fault shall be able to cause a sustained overvoltage
condition on any or all outputs. The supply shall provide
latch-mode overvoltage protection as defined below.


I understand that separating the two functions (OVS and OVP) gives
added security, but I can't see the need for a brute-force approach to
OVP. By this I mean that it is not necessary to clamp the output with
an expensive high-current zener or SCR - one can much more elegantly
achieve the same end, and still comply with Intel's spec, by turning
off the PWM controller, or by turning off its drive transistors. See
this DTK PSU which implements OVS, OVP and OPP with about $2 worth of
parts:

http://www.pavouk.comp.cz/hw/en_atxps.html

I have a 1000W minicomputer SMPS whose control module senses the
output and shuts off the oscillator in the event of an OV fault. There
are no expensive OVP parts, and this is in an SMPS that has 4 or 5
screw terminal capacitors the size of soft drink cans, stud mounted
diodes on massive heatsinks, four TO3 chopper transistors, and an AC
fan. The +5V cables (+5V @ 150A) are thick enough to start my car.

Nothing new in this requirement. However when dumping
product into a marketplace dominated by 'bean counter'
mentalities, then profits are just too great. How to suspect
a defective power supply? No long list of numerical
specification and no specific listing of overvoltage
protection? Then it is a power supply for the market of 'bean
counting' computer assemblers.


Some TV sets use 130V protection zeners (eg R2M, R2KY, $1.85 retail)
on their 100-115V supply rails. These designs have no OVS. Ironically
it appears that the designers have chosen this sledgehammer approach
because it costs *less* than OVS. I'm not really comfortable with such
a design because its success depends on the failure mode of the
protection device. IME the zener always fails SC, and therefore
protects the TV, but if it fails OC (unlikely, but possible), then
there is no protection at all. Killing the oscillator would be much
safer. In fact, HV protection and beam current limiting is usually
implemented by shutting down the horizontal oscillator.

I guess a comparable analogy may be MOVs in "surge protected" power
boards. They may sacrificially absorb the first surge, but thereafter
they are useless.

That schematic is further proof that many power supplies are
missing essential functions.


Sorry, I don't see it. You state that the original IBM supplies had an
OVP circuit, but you don't elaborate. How exactly did they do this? I
have the original IBM AT Tech Ref Manual but it doesn't adequately
spell out the PSU spec. Can you recommend one upmarket PSU that
handles OVP by brute-forcing the output(s)?

Some power supplies fail and
then destroy computer peripherals.


True. I witnessed a discussion at aus.electronics where an SMPS failed
in such a manner that AC leaked into the DC side of the switchmode
transformer, causing catastrophic damage to the PC. I suggested that
an external crowbar circuit could provide protection against such
disasters but the responses were negative.

A failure directly
traceable to a human who buys on price rather than learn basic
electrical principles. In a market where so many 'experts'
don't even know how how electricity works, then many clone
computers do have $25 power supplies.


What I find hard to comprehend is how even the upmarket ATX PSUs can
deliver their claimed power given the relative size of the components
in my 1000W SMPS. For example, when comparing the mains filter caps,
one is the size of a Coke can, the other is smaller than a C size
battery. Has technology really improved that much?


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
  #23  
Old April 12th 05, 12:05 PM
w_tom
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Posts: n/a
Default

You are assuming a power supply controller will see all
failures and then shutdown accordingly. What happens when
controller's feedback fails? A feedback circuit that will be
discussed again below. Power supply controller outputs more
power trying to raise a voltage that never rises. IOW power
supply has output excessive and destructive voltages. Just
another reason why "separate and distinct" overvoltage
protection has been required 30 years ago as it still is
required today.

Neither you nor I care how a particular power supply meets
this 'well proven to be necessary' OVP function. We don't
even care if the function uses a simple and easily constructed
crowbar or uses something different. The point remains a power
supply must provide that defined function. Schematic from
electro-tech.narod.ru quite obviously violates the industry
requirement. It has no overvoltage protection. It
demonstrates how power supplies are sold for well under $60
retail. They forget to include essential functions such as
OVP. That supply from http://electro-tech.narod.ru is
designed to be dumped into a market driven by 'bean counter'
engineering.

Provided were numeric specs for a supply that does provide
the OVP circuit. Back to the original point. Properly
designed supply does not and can not sell for $25 retail. So
how do others sell power supplies for $25 retail? They forget
to include required and necessary functions such as
Overvoltage Protection.

Is this done by a crowbar circuit or by some other means?
Neither you nor I care. Industry standards demand that OVP
function exist for 'long proven' necessary reasons. Some
supplies do provide such functions. But these minimally
acceptable supplies cannot sell for $25 retail - again
repeating the bottom line point.

In the meantime, that DTK PSU from www.pavouk.comp.cz
violates another essential function. The power supply must
provide galvanic isolation of at least 1000 volts. Therefore
the "Feedback" circuit must contain an optocoupler or
something equivalent. The DTK PSU has no such isolation. It
violates another industry standard. And so another essential
function would be 'forgotten'.

Earlier a power supply controller would output overvoltage
because the feedback circuit failed. Controller never knew it
was outputting excessive voltage. What feedback components?
Same optocoupler that is required with galvanic isolation.
Just another missing specification to sell at $25. Again the
point. Power supplies missing essential functions and
routinely dumped into the market because so many computer
assemblers don't even have basic electrical knowledge; never
learned about galvanic isolation, overvoltage protection,
feedback current limiting, or overpower protection.

When a computer assembler looks only at power and price,
then a game of specmanship is afoot. For example, a Dell or
HP power supply may claim only 250 watts. The 'bean counting'
computer assembler then claims that is woefully too small.
And yet if the same power supply was being marketed by others
to computer assemblers, then suddenly the same supply is rated
at 375 watts. Why? They don't list the output power. Rated
is maximum power that a power supply might consume. The 'bean
counting' computer assembler then declares the HP and Dell
supplies are undersized.

It gets even more interesting. A power supply must be
completely shorted out and still must not be damaged. And yet
here are power supplies, designed for a 'bean counter' market,
that self destruct even before reaching 100% load:
http://www6.tomshardware.com/howto/0...021/index.html

First thing to look for in any power supply: if the supply
manufacturer does not provide a long list of numerical specs,
then bet it is a scam. More responsible power supply
manufacturers provide numerous numerical specs. One need not
even know what those specs mean. Just having written numerical
specs is a first requirement. Manufacturer commits; says to
the 1% who know technology that this supply does provide these
functions. However a manufacturer who is dumping inferior
supplies into a market of computer assemblers must disempower
the 1%. He must provide no written specifications. Then a
knowledgeable 1% cannot warn the other 99% of a defective
product.

Welcome to a world where so many power supplies don't
provide specs and are then recommended based only on the price
and watts.

#1 requirement for a power supply: it must provide a long
list of numeric specs. If that power supply does not
specifically state overvoltage protection, then another
essential function is missing.

We care less how he provides overvoltage protection. We
care more that he claims to provide OVP. That missing
function demonstrates why so many supplies sell for only $25
and $40 full retail.

Franc Zabkar wrote:
On Mon, 11 Apr 2005 19:35:21 -0400, w_tom put
finger to keyboard and composed:
...

I understand that separating the two functions (OVS and OVP) gives
added security, but I can't see the need for a brute-force approach to
OVP. By this I mean that it is not necessary to clamp the output with
an expensive high-current zener or SCR - one can much more elegantly
achieve the same end, and still comply with Intel's spec, by turning
off the PWM controller, or by turning off its drive transistors. See
this DTK PSU which implements OVS, OVP and OPP with about $2 worth of
parts:

http://www.pavouk.comp.cz/hw/en_atxps.html

I have a 1000W minicomputer SMPS whose control module senses the
output and shuts off the oscillator in the event of an OV fault. There
are no expensive OVP parts, and this is in an SMPS that has 4 or 5
screw terminal capacitors the size of soft drink cans, stud mounted
diodes on massive heatsinks, four TO3 chopper transistors, and an AC
fan. The +5V cables (+5V @ 150A) are thick enough to start my car.
...

Some TV sets use 130V protection zeners (eg R2M, R2KY, $1.85 retail)
on their 100-115V supply rails. These designs have no OVS. Ironically
it appears that the designers have chosen this sledgehammer approach
because it costs *less* than OVS. I'm not really comfortable with such
a design because its success depends on the failure mode of the
protection device. IME the zener always fails SC, and therefore
protects the TV, but if it fails OC (unlikely, but possible), then
there is no protection at all. Killing the oscillator would be much
safer. In fact, HV protection and beam current limiting is usually
implemented by shutting down the horizontal oscillator.

I guess a comparable analogy may be MOVs in "surge protected" power
boards. They may sacrificially absorb the first surge, but thereafter
they are useless.
...

Sorry, I don't see it. You state that the original IBM supplies had an
OVP circuit, but you don't elaborate. How exactly did they do this? I
have the original IBM AT Tech Ref Manual but it doesn't adequately
spell out the PSU spec. Can you recommend one upmarket PSU that
handles OVP by brute-forcing the output(s)?
...

True. I witnessed a discussion at aus.electronics where an SMPS failed
in such a manner that AC leaked into the DC side of the switchmode
transformer, causing catastrophic damage to the PC. I suggested that
an external crowbar circuit could provide protection against such
disasters but the responses were negative.
...

What I find hard to comprehend is how even the upmarket ATX PSUs can
deliver their claimed power given the relative size of the components
in my 1000W SMPS. For example, when comparing the mains filter caps,
one is the size of a Coke can, the other is smaller than a C size
battery. Has technology really improved that much?

- Franc Zabkar

  #24  
Old April 13th 05, 08:08 AM
Franc Zabkar
external usenet poster
 
Posts: n/a
Default

On Tue, 12 Apr 2005 07:05:18 -0400, w_tom put
finger to keyboard and composed:

You are assuming a power supply controller will see all
failures and then shutdown accordingly.


I did write that "I understand that separating the two functions (OVS
and OVP) gives added security", so I understand that there are some
caveats with a single-chip approach.

What happens when
controller's feedback fails?


In most cases the OVS circuitry will detect an OV condition and shut
down the oscillator. I've actually seen such faults in other PSUs, eg
when optocouplers or feedback transformers or sense resistors go OC.
One potential problem with single-chip solutions is if the internal
reference voltage is shared by both the OVS logic and the PWM
regulator. In such cases a fault in the voltage reference may cause
catastrophic damage. Having said that, it may still be possible to
separate these two functions within the same IC. In any case the DTK
circuit I alluded to *does* separate these functions and *does* comply
with Intel's spec. And it does this at the cost of a few small-signal
transistors, diodes, and passives. In fact the BOM for the OV, PG, and
PWM circuits would cost about $1 or $2.

http://focus.ti.com/docs/prod/folders/print/tl494.html
$0.23 /1000

http://focus.ti.com/docs/prod/folders/print/lm393.html
$0.16 /1000

Neither you nor I care how a particular power supply meets
this 'well proven to be necessary' OVP function. We don't
even care if the function uses a simple and easily constructed
crowbar or uses something different. The point remains a power
supply must provide that defined function. Schematic from
electro-tech.narod.ru quite obviously violates the industry
requirement. It has no overvoltage protection.


It *does* have OVP. It's just that the implementation does not appear
to rigidly follow Intel's spec. For example, if I interfere with the
+5V feedback by removing R62 from pin 14, the output voltages will
rise to a point where the OVS pins (3,4,6) will trigger a shutdown of
the oscillator.

Provided were numeric specs for a supply that does provide
the OVP circuit.


Specs can lie, or at least be deceiving. A high price does not
guarantee quality or spec compliance.

Is this done by a crowbar circuit or by some other means?
Neither you nor I care.


On the contrary, I do. At the very least, knowing how a certain
function is implemented can explain any differences in price. For
example, if each of the major rails were shunted by high current SCRs
or protection zeners, then one could expect to pay a much higher
price. OTOH, if OVS and OVP were implemented with 50c ICs, then one
would not expect such functions to impact noticeably on the overall
cost.

In the absence of specific examples from you, I'm left to examine
various PSUs at this website:

http://terasan.okiraku-pc.net

Unfortunately the site is in Japanese, but there is just enough info
to ascertain the inner workings of both low-end and high-end ATX PSUs.

For example, Antec's TruePower 550 is pictured and described he
http://terasan.okiraku-pc.net/dengen/no57/

The ICs of interest are the UC3844 PWM regulator and the TPS3510 PSU
supervisor:

http://www.st.com/stonline/books/pdf/docs/4299.pdf
http://focus.ti.com/lit/ds/symlink/tps3510.pdf

The costs a

http://focus.ti.com/docs/prod/folder...t/tps3510.html
$0.45 /1000

http://focus.ti.com/docs/prod/folders/print/uc3844.html
$0.80 /1000

The TPS3510 IC implements OVS, UVS, OVP, UVP, and PG. I suspect its
Fault Protection Output pin controls the UC3844 regulator. There
appear to be no other OVP parts.

Another manufacturer, PC Power & Cooling, uses the TPS5510 supervisor
IC in its Turbo-Cool 450ATX:
http://terasan.info/dengen/no041/
http://focus.ti.com/lit/ds/symlink/tps5510.pdf

Industry standards demand that OVP
function exist for 'long proven' necessary reasons. Some
supplies do provide such functions. But these minimally
acceptable supplies cannot sell for $25 retail - again
repeating the bottom line point.


That may be true, but if we were to use your definition of OVP, then
some, if not all, branded PSUs do not provide this function either.

In the meantime, that DTK PSU from www.pavouk.comp.cz
violates another essential function. The power supply must
provide galvanic isolation of at least 1000 volts. Therefore
the "Feedback" circuit must contain an optocoupler or
something equivalent. The DTK PSU has no such isolation. It
violates another industry standard. And so another essential
function would be 'forgotten'.


The regulator and the feedback circuit exist on the same side of the
PSU, ie on the DC side. Therefore no "galvanic isolation" is required
between the two. In any case, isolation between the AC and DC sections
is provided by transformers, at least when high currents are involved.
AFAICS, cheap optocouplers are only used in the 5VSB circuit, if at
all. In the DTK case, no special feedback is required in the 5VSB
section because the 78L05 linear regulator doesn't require it. OTOH,
the LC-B250ATX uses an optically isolated TL431 voltage reference to
achieve the same end. The Antec Truepower PSUs appear to do it this
way, too. All three PSU designs are "galvanically isolated" where
needed.

When a computer assembler looks only at power and price,
then a game of specmanship is afoot.


That works both ways. Ignorant people assume that a higher price means
higher quality. They have never heard of "badge engineering". That's
where an up-market vendor/manufacturer rebadges a down-market product
and extracts a price premium by leveraging his reputation rather than
his technical expertise.

For example, a Dell or
HP power supply may claim only 250 watts. The 'bean counting'
computer assembler then claims that is woefully too small.
And yet if the same power supply was being marketed by others
to computer assemblers, then suddenly the same supply is rated
at 375 watts. Why? They don't list the output power. Rated
is maximum power that a power supply might consume. The 'bean
counting' computer assembler then declares the HP and Dell
supplies are undersized.


I have to agree. In fact my own measurements lead me to believe that
typical Athlon and P4 systems will never draw more than 150W.

It gets even more interesting. A power supply must be
completely shorted out and still must not be damaged. And yet
here are power supplies, designed for a 'bean counter' market,
that self destruct even before reaching 100% load:
http://www6.tomshardware.com/howto/0...021/index.html


The first thing that caught my eye was this:

"We've ... now decided to tackle this volatile subject with testing of
21 different, high-end power supplies in the THG lab in Munich,
Germany. In spite of the high end-user retail prices, our lab
technicians were surprised by the test results. No fewer than 6 power
supplies struggled under full load: 3 of the candidates simply went up
in smoke, while the other 3 shut down prematurely."

It seems that price, specs and reputation are no guarantee of
performance. ;-)

This also caught my eye:

"Our attempt to test the Noise Magic power supply had disastrous
consequences. This is a modified Enermax unit fitted with a Papst fan.
It stopped working after one minute. When we tried to switch it back
on again after a suitable delay, it simply burned out."

I would have thought that even a badge engineered Enermax was not a
"bean counter's" PSU ;-)

Anyway, you have introduced a new subject, namely overload protection.
OVP is cheap to implement, but sensing current is more difficult than
sensing voltage, so I would expect that many manufacturers would take
shortcuts here. The aforementioned LC and DTK PSUs both sense a
voltage at the drive transformer, whereas other PSUs monitor the
current flow in the chopper transistor(s). I'm not sure that's the way
the Antec 550W PSU does it, but its UC3844 PWM controller *does* have
a current sense pin. The application circuit shows this pin connected
to a current transformer. My 1000W minicomputer PSU also uses a
current transformer in the chopper circuit to indirectly sense the
load current. I suspect that the OPP circuits in cheaper PSUs (such as
the LC and DTK) would be able to respond correctly to dead shorts, but
not necessarily to overloads.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
  #25  
Old September 1st 05, 01:57 AM
Jon
external usenet poster
 
Posts: n/a
Default

"U. Cortez" said

I believe a power surge toasted my power supply the other day, so I
replaced it with a new 350W ATX PSU. After removing the burnt psu, I
screwed the new psu into the case, hooked the ATX power supply to the
motherboard, and hooked up power for various components (HD's,
CD-ROM's). The motherboard's pilot light turns on to signify that it's
getting power, but when I press the case's power button... nothing. No
fans, no sound, no disk spinning, no signs of life at all (besides that
pilot light being on). Am I forgetting something?

I inspected all the components (and the motherboard and cpu) and none
of them appear (or smell) to have been damaged.

Where do I go from here? Any help would be appreciated.

Motherboard: DFI AK70 (AMD 750 cpu).

-U.

PS, forgive the cross-post -- I don't have a news host and google is
giving me errors when I try to post to some of these groups
individually.


  #26  
Old September 1st 05, 05:00 AM
CJT
external usenet poster
 
Posts: n/a
Default

Jon wrote:
"U. Cortez" said


I believe a power surge toasted my power supply the other day, so I
replaced it with a new 350W ATX PSU. After removing the burnt psu, I
screwed the new psu into the case, hooked the ATX power supply to the
motherboard, and hooked up power for various components (HD's,
CD-ROM's). The motherboard's pilot light turns on to signify that it's
getting power, but when I press the case's power button... nothing. No
fans, no sound, no disk spinning, no signs of life at all (besides that
pilot light being on). Am I forgetting something?

I inspected all the components (and the motherboard and cpu) and none
of them appear (or smell) to have been damaged.

Where do I go from here? Any help would be appreciated.

Motherboard: DFI AK70 (AMD 750 cpu).

-U.

PS, forgive the cross-post -- I don't have a news host and google is
giving me errors when I try to post to some of these groups
individually.



If your MB has the 4-pin (square) auxiliary power connector, and you
haven't connected it, you will get that result.

Another possibility is that, while changing the PS, you accidentally
disconnected the power button connector. It's small and easy to
pull off its header.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .
  #27  
Old September 1st 05, 10:39 PM
Peter Emanuelsson
external usenet poster
 
Posts: n/a
Default

On Thu, 01 Sep 2005 04:00:04 GMT, in comp.sys.ibm.pc.hardware.systems,
CJT wrote:

Jon wrote:
"U. Cortez" said

I believe a power surge toasted my power supply the other day, so I
replaced it with a new 350W ATX PSU. After removing the burnt psu, I
screwed the new psu into the case, hooked the ATX power supply to the
motherboard, and hooked up power for various components (HD's,
CD-ROM's). The motherboard's pilot light turns on to signify that it's
getting power, but when I press the case's power button... nothing. No
fans, no sound, no disk spinning, no signs of life at all (besides that
pilot light being on). Am I forgetting something?

I inspected all the components (and the motherboard and cpu) and none
of them appear (or smell) to have been damaged.

Where do I go from here? Any help would be appreciated.

Motherboard: DFI AK70 (AMD 750 cpu).

-U.

PS, forgive the cross-post -- I don't have a news host and google is
giving me errors when I try to post to some of these groups
individually.


If your MB has the 4-pin (square) auxiliary power connector, and you
haven't connected it, you will get that result.

Another possibility is that, while changing the PS, you accidentally
disconnected the power button connector. It's small and easy to
pull off its header.


A mistake people make every now and then (including myself, and I've
assembled lots of computers) is to set the FDD power connector one
step to the side (only connecting three of the four pins), and this
will cause a shortcut.

Another possibility is that something else is dead too. All defects
aren't visible to the naked eye...

Disconnect all power cables except the one to the motherboard, and
also disconnect the IDE and FDD cables (a defective drive can prevent
a computer from starting).

Then try to start the comp again.

If it works now, start reconnecting components one by one, and do a
test start between each...

If it doesn't start even with all drives etc disconnected, your mobo
might be fried. Or maybe your new PSU is defective too. Or something
else...

--
May all spammers die in horrible pains!
Wanna e-mail me? Well, peter_e is correct, but the rest is obviously bogus...
Try algonet in the .se TLD instead.
  #28  
Old September 2nd 05, 12:31 AM
PWY
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"Peter Emanuelsson" wrote in message
...
On Thu, 01 Sep 2005 04:00:04 GMT, in comp.sys.ibm.pc.hardware.systems,
CJT wrote:

Jon wrote:
"U. Cortez" said

I believe a power surge toasted my power supply the other day, so I
replaced it with a new 350W ATX PSU. After removing the burnt psu, I
screwed the new psu into the case, hooked the ATX power supply to the
motherboard, and hooked up power for various components (HD's,
CD-ROM's). The motherboard's pilot light turns on to signify that it's
getting power, but when I press the case's power button... nothing. No
fans, no sound, no disk spinning, no signs of life at all (besides that
pilot light being on). Am I forgetting something?

I inspected all the components (and the motherboard and cpu) and none
of them appear (or smell) to have been damaged.

Where do I go from here? Any help would be appreciated.

Motherboard: DFI AK70 (AMD 750 cpu).

-U.

PS, forgive the cross-post -- I don't have a news host and google is
giving me errors when I try to post to some of these groups
individually.

If your MB has the 4-pin (square) auxiliary power connector, and you
haven't connected it, you will get that result.

Another possibility is that, while changing the PS, you accidentally
disconnected the power button connector. It's small and easy to
pull off its header.


A mistake people make every now and then (including myself, and I've
assembled lots of computers) is to set the FDD power connector one
step to the side (only connecting three of the four pins), and this
will cause a shortcut.

Another possibility is that something else is dead too. All defects
aren't visible to the naked eye...

Disconnect all power cables except the one to the motherboard, and
also disconnect the IDE and FDD cables (a defective drive can prevent
a computer from starting).

Then try to start the comp again.

If it works now, start reconnecting components one by one, and do a
test start between each...

If it doesn't start even with all drives etc disconnected, your mobo
might be fried. Or maybe your new PSU is defective too. Or something
else...

--
May all spammers die in horrible pains!
Wanna e-mail me? Well, peter_e is correct, but the rest is obviously
bogus...
Try algonet in the .se TLD instead.


On the back of the power supply, there is a switch where voltage can be set
to either 120 volts or 240 volts. Make sure it is set to the correct
voltage. This often overlooked.

 




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