Power supply, but no power???

On Fri, 08 Apr 2005 17:19:23 GMT, Wes Newell
put finger to keyboard and composed:

On Fri, 08 Apr 2005 12:22:21 -0400, w_tom wrote:

Any power supply that fails must not damage any other
computer part. But if the essential function was missing in
that supply, then you now may have other damage. A minimally
acceptable supply sells for about $65 full retail. Supplies
missing essential functions such as overvoltage protection
sell for less, earn greater profits for their manufacturers,
and can then cause disk drive and motherboard failure.

I think overload protection is a requirement for UL approval. And I've
never spent over $24 for a PSU.:-)

I've used a 600W similar to this for over a year now on my A64 system. But
it was $24 when I bought mine.

http://store.mrtechus.com/60ulapatxcop.html

I'd be suspicious of that 600W rating. The combined output of the 3
major rails is 644W, a figure that doesn't appear to allow for proper
derating. If it's a Deer brand PSU, I'd be looking especially closely
at it. I've been stung by a 170W fake labelled as 400W.

Here are the claimed specs from the above URL:

================================================== =================
ATX 600 Watt Power Supply for P4 ,PIII and AMD processor compatible
with ATX 2.03 standard.

DC Output:

+5V 50A +/-5% +3.3V 32A +/-4% +12V 24A +/-5%

-12V 1.0A +/-10% -5V 0.5A +/-10% +5Vsb 2.0A +/-5%
================================================== =================

Having said the above, I'd be willing to bet that the PSU in a typical
system is never called upon to provide more than about 150W.

Until my recent experience with the fake PSU, I've always been well
served by generics. In fact, I contacted a dozen or so computer stores
in my area and was unable to find a single vendor who could supply
anything other than a generic ATX PSU. Most were selling Deers. I had
to go online to find a branded PSU.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

Overvoltage protection is not required for UL approval -
obviously.

First, power supplies selling for $25 retail would quickly
forget that essential function. If is contains essential
functions such as overvoltage protection, then the
manufacturer would proudly note that function - and many
others. If is does not list overvoltage protection (as with
most sub $40 supplies), then it will also forget to install
overvoltage protection and many other essential functions.

Second, just not possible to sell a supply at $25 retail,
earn a profit, and include essential functions.

Third, UL only cares about you getting hurt. UL does not
care for an instant how destructive that power supply is to
any transistors. Overvoltage protection does nothing for
human safety.

Fourth, then there is the common problem with counterfeit UL
stickers. No way a $25 supply is going to include functions
considered essential even 30 years ago.

Wes Newell wrote:
On Fri, 08 Apr 2005 12:22:21 -0400, w_tom wrote:
Any power supply that fails must not damage any other
computer part. But if the essential function was missing in
that supply, then you now may have other damage. A minimally
acceptable supply sells for about $65 full retail. Supplies
missing essential functions such as overvoltage protection
sell for less, earn greater profits for their manufacturers,
and can then cause disk drive and motherboard failure.

I think overload protection is a requirement for UL approval. And I've
never spent over $24 for a PSU.:-)

I've used a 600W similar to this for over a year now on my A64
system. But it was $24 when I bought mine.

http://store.mrtechus.com/60ulapatxcop.html

Problem could even been created by a motherboard standoff
shorted through solder mask. Example of why one does not swap
parts. You fixed (permanently or temporarily) the problem and
don't even know why it existed. In the future, get the
numbers before disassembling anything. At least we would have
a much short list of suspects. If failure is seen on meter,
then you could disconnect some things and test until the
problem is resolved. Knowing which voltage was problematic
could have also been more helpful.

Just a better way to approach the problem next time.
Historically, such intermittents tend to return slightly more
often than not.

"U. Cortez" wrote:
Well last night I tested the power supply (with it just plugged into
the motherboard) and all the voltages were in their acceptable ranges.
So, I started to plug things back in 1 at a time, and... it all
worked! I'm typing this now on my working computer. There must have
just been a loose connection or something when I first installed my new
PSU. But when I took my computer apart (yes, I mean completely apart
-- even took the cooler off the cpu) and put it back together I must
have secured whatever was keeping it from starting up before.

So I guess the failed motherboard was a false alarm (whew!). Now the
first thing on my agenda: get a UPS so I don't have to worry about
circuit trips blowing my PSU again.

Thanks all for the help!

-U.

On Sun, 10 Apr 2005 06:07:31 -0400, w_tom wrote:

Overvoltage protection is not required for UL approval -
obviously.

If you say so.

Second, just not possible to sell a supply at $25 retail,
earn a profit, and include essential functions.

So, you don't think they could spent an extra 25 cents to do this in a $25
PSU. Interesting.

Third, UL only cares about you getting hurt. UL does not
care for an instant how destructive that power supply is to any
transistors. Overvoltage protection does nothing for human safety.

Again, if you say so.

Fourth, then there is the common problem with counterfeit UL
stickers. No way a $25 supply is going to include functions considered
essential even 30 years ago.

Well, This psu says it has overload protection, and I have no basis for
calling them liars. It's retail price is over $40, but it's sale price is
only $18. They also have a 300W unit that states it has overload
protection they sell for $9 (Retail price of $24).

http://store.mrtechus.com/60ulapatxcop.html

--
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My server http://wesnewell.no-ip.com/cpu.php
Verizon server http://mysite.verizon.net/res0exft/cpu.htm

I think you both have a point. I have no doubt that there are cheap
psu's out there that completely ignore the need for overvoltage
protection. On the contrary, there are probably some inexpensive psu's
that have the protection. While it appears that the psu that wes found
does have protection, I'd still be a little skeptical of a psu that
claims to push 600w but only cost $18. Personally, I'll stick with
name-brand psu's.

Overload protection is another and different function
required of power supplies. Does that $25 supply really have
overload protection? The specs are quite clear about this.
Short all outputs together and turn on power. Power supply
must not be damaged. That demonstrates overload protection
which is completely different from overvoltage protection
which, in turn, has nothing to do with UL approval.

This is basic electrical knowledge that anyone should
understand before making power supply recommendations.
Overvoltage and overload (or overpower) protection are
completely different functions. Power supplies must meet
both, and other standards such as FCC. Just another standard
that many discounted power supplies may violate to sell at
profit.

Wes Newell wrote:
On Sun, 10 Apr 2005 06:07:31 -0400, w_tom wrote:
Overvoltage protection is not required for UL approval -
obviously.

If you say so.

Second, just not possible to sell a supply at $25 retail,
earn a profit, and include essential functions.

So, you don't think they could spent an extra 25 cents to do this
in a $25 PSU. Interesting.

Third, UL only cares about you getting hurt. UL does not
care for an instant how destructive that power supply is to any
transistors. Overvoltage protection does nothing for human safety.

Again, if you say so.

Fourth, then there is the common problem with counterfeit UL
stickers. No way a $25 supply is going to include functions
considered essential even 30 years ago.

Well, This psu says it has overload protection, and I have no basis
for calling them liars. It's retail price is over $40, but it's
sale price is only $18. They also have a 300W unit that states it
has overload protection they sell for $9 (Retail price of $24).

http://store.mrtechus.com/60ulapatxcop.html

On Sun, 10 Apr 2005 11:38:53 GMT, Wes Newell
put finger to keyboard and composed:

On Sun, 10 Apr 2005 06:07:31 -0400, w_tom wrote:

Overvoltage protection is not required for UL approval -
obviously.

If you say so.

Second, just not possible to sell a supply at $25 retail,
earn a profit, and include essential functions.

So, you don't think they could spent an extra 25 cents to do this in a $25
PSU. Interesting.

In fact the additional cost can be nil. Deer PSUs have a single IC
that does it all - PWM control, PS-ON control, +3.3V regulation,
+5/+12V regulation, Power Good generation, and overvoltage sensing.

See this circuit diagram:

"LC-B250ATX ch. Y-B200-ATX ver. 2.9 JNC Computer Co."
http://electro-tech.narod.ru/schemat...Y-B200-ATX.zip


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

On Mon, 11 Apr 2005 06:41:58 +1000, Franc Zabkar
put finger to keyboard and composed:

On Sun, 10 Apr 2005 11:38:53 GMT, Wes Newell
put finger to keyboard and composed:

On Sun, 10 Apr 2005 06:07:31 -0400, w_tom wrote:

Overvoltage protection is not required for UL approval -
obviously.

If you say so.

Second, just not possible to sell a supply at $25 retail,
earn a profit, and include essential functions.

So, you don't think they could spent an extra 25 cents to do this in a $25
PSU. Interesting.

In fact the additional cost can be nil. Deer PSUs have a single IC
that does it all - PWM control, PS-ON control, +3.3V regulation,
+5/+12V regulation, Power Good generation, and overvoltage sensing.

Here is the data for an all-in-one IC (not the same as in the Deer
PSU):
http://www.systemgeneral.com/semiGP/sg6105_E.asp


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

I don't see the overvoltage protection circuit anywhere in
that power supply at electro-tech.narod.ru . Overvoltage
protection means something must be able to short out a (about)
25 amp output with no damage. Not a cheap component and
definitely not possible inside an Integrated Circuit.

The IC SG6105 contains many functions previously performed
by multiple chips. This is a minor cost decrease. But, for
example, the galvanic isolation necessary for some of those
functions is not inside this chip either. Things such as
optocoupler are still another separate component.
Overvoltage protection is not a part of that chip. In fact,
Intel specs demand that overvoltage protection be part of a
separate circuit.

The SG6105 does contain circuits once provided by multiple
inexpensive components. A power supply once selling for less
than $100 now costs only $65 retail. Expensive components are
still required for other and necessary functions such as
overvoltage protection. Supplies containing necessary
functions such as overvoltage protection cannot sell for $25
retail at profit. Those would be supplies dumped into the
market missing essential functions.

Franc Zabkar wrote:
In fact the additional cost can be nil. Deer PSUs have a single IC
that does it all - PWM control, PS-ON control, +3.3V regulation,
+5/+12V regulation, Power Good generation, and overvoltage sensing.

See this circuit diagram:

"LC-B250ATX ch. Y-B200-ATX ver. 2.9 JNC Computer Co."
http://electro-tech.narod.ru/schemat...Y-B200-ATX.zip

On Mon, 11 Apr 2005 14:35:39 -0400, w_tom put
finger to keyboard and composed:

I don't see the overvoltage protection circuit anywhere in
that power supply at electro-tech.narod.ru . Overvoltage
protection means something must be able to short out a (about)
25 amp output with no damage.

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.

Not a cheap component and
definitely not possible inside an Integrated Circuit.

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 IC SG6105 contains many functions previously performed
by multiple chips. This is a minor cost decrease. But, for
example, the galvanic isolation necessary for some of those
functions is not inside this chip either. Things such as
optocoupler are still another separate component.
Overvoltage protection is not a part of that chip. In fact,

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.

Intel specs demand that overvoltage protection be part of a
separate circuit.

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.

The SG6105 does contain circuits once provided by multiple
inexpensive components. A power supply once selling for less
than $100 now costs only $65 retail. Expensive components are
still required for other and necessary functions such as
overvoltage protection. Supplies containing necessary
functions such as overvoltage protection cannot sell for $25
retail at profit. Those would be supplies dumped into the
market missing essential functions.

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?

Franc Zabkar wrote:
In fact the additional cost can be nil. Deer PSUs have a single IC
that does it all - PWM control, PS-ON control, +3.3V regulation,
+5/+12V regulation, Power Good generation, and overvoltage sensing.

See this circuit diagram:

"LC-B250ATX ch. Y-B200-ATX ver. 2.9 JNC Computer Co."
http://electro-tech.narod.ru/schemat...Y-B200-ATX.zip


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.