fake PC supplies

[Paul Burke]

Pooh Bear wrote:

a) Probably because no-one actually *needs* a 500W power supply and the
dodgy suppliers know this.

b) Because it's possible to cheat and lie. Enron did this rather
dramatically for example.

An example of Gresham's Law in action. Then it concerned bad money
driving out good; now it's bad products. Look at what happened to floppy
disks- the drive for low price reduced the quality BELOW the minimum
required for safe data storage. Nobody wants to spend $1 each on
floppies like we did not-so-many-years-ago. If I need to use one these
days, I've got a box of 10-15 year old ones that I recycle. They are
still better than buying new.

Similar thing has happened to food. Supermarkets sell cheap crap, small
shops selling good stuff at 1.5 times the price go out of business (then
the price of the crap goes up too).

Paul Burke

 

[Ian Stirling]

Mike Monett <no@spam.com> wrote:

Ian Stirling wrote:

[...]

I wonder about a 'gentler' way.
If you simply disconnect the main energy storage cap, then the supply
won't stay pumping power into the output caps for more than a few
microseconds.

Yes, I as thinking along the same line. What about a separate unit that
monitors the voltages, crowbars them in case of a fault, and removes
the ac power to the computer?

Unfortunately, that's not quite the same thing.
The energy storage cap holds perhaps 5+ Joules of energy, which would be
plenty to spike the output voltages quite high, in case of a malfunction,
even if you disconnect the AC.

 

[Mike Monett]

Ian Stirling wrote:

Mike Monett <no@spam.com> wrote:
Ian Stirling wrote:

[...]

I wonder about a 'gentler' way.
If you simply disconnect the main energy storage cap, then the supply
won't stay pumping power into the output caps for more than a few
microseconds.

Yes, I as thinking along the same line. What about a separate unit that
monitors the voltages, crowbars them in case of a fault, and removes
the ac power to the computer?


Unfortunately, that's not quite the same thing.
The energy storage cap holds perhaps 5+ Joules of energy, which would be
plenty to spike the output voltages quite high, in case of a malfunction,
even if you disconnect the AC.

A healthy crowbar should fix that

Mike Monett

 

[Guy Macon]

Content-Transfer-Encoding: 8Bit


Clifford Heath wrote:

R Adsett wrote:

The love of money is the root of all evil!
The quote makes more sense when it's complete.

Quite. The quote is:
"The love of money is the root of all *kinds of* evil".
Quite different again... and spectacularly different
from the oft misquoted version.

Normally I silently killfile anyone who is rude enough to hijack
a discussion about electronics in an electronics newsgroup and
turn it into another boring religion/politics discussion, but
just this once I will correct the rude posters.

To be 100% accurate, you are both wrong. The actual quote is:
Rhiza gar pas ho kakos esti ejstiv ho philarguria (Or, if your
newsreader handles greek fonts, rJivza gavr pa'ß oJ kakovß oJ
filarguriva).

When a Bible passage is quoted, the default assumption is that
it's the King James Version. A distant second assumption is
the New Internation Version, with all the others tied for last
as far as being the default assumption for quotes goes.

King James Version:
For the love of money is the root of all evil

New International Version:
For the love of money is a root of all kinds of evil

R Adsett wasn't doing anything wrong by quoting the default
english translation. Clifford Heath should not have "corrected"
him by quoting another translation as if R Adsett had got the
quote wrong - especially without saying what translation he
himself was using. He also should have corrected the entire
quote; he got "all kinds of evil" but missed "a root."

That being said, this is a passage where the changes in english
language since the 1600s has changed the meaning for the modern
reader. When the KJV says "the root of all evil", the 15th
century reader understood it as meaning what a 21st century
reader would get from "a root of all kinds of evil". Note that
the difference between "a root" and "the root" is significant.

My ancient Greek is quite rusty and wasn't all that good in the
first place, but from my reading, "a root of all kinds of evil"
best conveys the sense of the original greek.

Can we go back to talking about electronics now? There are
hundreds of newsgroups dedicated to religion, but only this
one that is devoted to electronics design. Do you people really
have to fill every newsgroup with religion and politics?

 

[Ian Stirling]

Paul Burke <paul@scazon.com> wrote:

Pooh Bear wrote:

a) Probably because no-one actually *needs* a 500W power supply and the
dodgy suppliers know this.

b) Because it's possible to cheat and lie. Enron did this rather
dramatically for example.

An example of Gresham's Law in action. Then it concerned bad money
driving out good; now it's bad products. Look at what happened to floppy
disks- the drive for low price reduced the quality BELOW the minimum
required for safe data storage. Nobody wants to spend $1 each on
floppies like we did not-so-many-years-ago. If I need to use one these
days, I've got a box of 10-15 year old ones that I recycle. They are
still better than buying new.

I'm not sure I agree.
I have approximately 1000 floppy disks, most of which are about 1995 vintage.
Of these, essentially none, not even the verbatim 'datalife' ones will
format without errors.

Last year, I broke open a box of IBM OS2/warp (1994), and extracted the
40 or so floppies.
None of them would format on any of 3 floppy drives I have.

 

[R Adsett]

In article <42928c9d$0$8120$afc38c87@news.optusnet.com.au>,
no@spam.please.net says...

R Adsett wrote:
The love of money is the root of all evil!
The quote makes more sense when it's complete.

Quite. The quote is:
"The love of money is the root of all *kinds of* evil".
Quite different again... and spectacularly different
from the oft misquoted version.

Umm, where are you getting that from? Not that I think they are that
different in intent.

1 Timothy 6:10
"For the love of money is the root of all evel: which while some coveted
after, they have erred from the faith, and pierced themselves through
with many sorrows"

That King James which would be from where the quote probably originally
entered the English language

Ah, the NIV translates as you've quoted. The version as I quoted would
still be correct though.

Robert

 

[R Adsett]

In article <1196a5gblcm6fc5@corp.supernews.com>,
_see.web.page_@_www.guymacon.com_ says...

To be 100% accurate, you are both wrong. The actual quote is:
Rhiza gar pas ho kakos esti ejstiv ho philarguria (Or, if your
newsreader handles greek fonts, rJivza gavr pa'ß oJ kakovß oJ
filarguriva).

Can we go back to talking about electronics now? There are
hundreds of newsgroups dedicated to religion, but only this
one that is devoted to electronics design. Do you people really
have to fill every newsgroup with religion and politics?

Actually, I was just reacting to a mis-quote that annoys me a bit. I
wasn't really trying to discuss it's contents but point taken.

Robert

 

[René]

On Mon, 23 May 2005 21:45:35 +1000, "Adam. Seychell"
<invald@invalid.com> wrote:

I'm recently seeing more cheap PC supplies on the market which appear to
be fake, in that the clammed output power not impossible for the size of
parts inside. e.g I have a 500W "Shaw" brand ATX supply, and its output
inductor uses a piddly T106 (26mm OD) core. The 5V is specified at
35Amps yet the output inductor winding is 2x1.2mm diam wire and the
rectifiers for the 5V is a 15Ax2 Schottky device. This is typical for
these very cheap power supplies. Similarly the 12V @ 18A output uses
2x8A diode (STPR1620).

I've also seen several other PC supplies that have completely omitted
EMC components, and simply used wire links where the CM inductors are
meant to go. Some PC supplies I've come across have even used standard
ceramic/polyester capacitors in place of the Y and X2 rated safety
capacitors.

How do they get away with this ?

Off course they use the same "commercial Watts" as utilized in those 2
x 150W wallplug-adaptor-fed PC speakers.

Perhaps it's "500W PMPO".

Makes me think of early computer monitors that would do 1600 x 1200
pix; and >100Hz refresh. They would indeed - but not at the same time.


--
- René

 

[Pooh Bear]

Mike Monett wrote:

Pooh Bear wrote:

Mike Monett wrote:

The Intel failure section is hilarious. I copied it below for those
who don't have the time to download it:

--------------------------------------------------------------------
3.1.5 Catastrophic Failure Protection

Should a component failure occur, the power supply should not
exhibit any of the following:

- Flame
- Excessive Smoke
- Charred PCB
- Fused PCB conductor
- Startling noise
- Emission of molten material

With the exception of *startling noise* - all that is covered by IEC60950.
Or UL1950 in your case.

[...]

Graham

Do you have a copy of UL1950 or IEC60950? According to this site, IEC60950
is $337.48 USD:

Yes those standards are pricey.

http://www.techstreet.com/cgi-bin/detail?product_id=930919

If you don't have copies, do you have another reference that discusses
failure protection?

I have a copy ( a few yrs old ) of BSEN60065 which is pretty similar to 60950.
Note : BSEN = the adopted British standard based on the IEC original. 60950 is
specifically IT equipment whereas 60065 is listed as audio and video equipment
now IIRC.

Graham

 

[Pooh Bear]

bigcat@meeow.co.uk wrote:

Adam. Seychell wrote:

The 5V is specified at
35Amps yet the output inductor winding is 2x1.2mm diam wire and the
rectifiers for the 5V is a 15Ax2 Schottky device. This is typical for

these very cheap power supplies. Similarly the 12V @ 18A output uses
2x8A diode (STPR1620).

The devices are in the forced air cooling stream. They are also
probably heatsunk.

They *have* to be heatsinked !

If it's a TO-220 device as I suspect, that package can only safely
dissipate 2W in typical free air conditions. That would make it good for
only 2 Amps.

Also they can be run at above recommended temps to some extent.

If you don't care about reliability ! It'll likely fail s/c.

Computer power supplies do not need to have a long life, since a new
puter will usually be passed after 12 years.

They have quite long enough life to need parts to be properly rated.

Graham

 

[Guy Macon]

R Adsett wrote:

Ah, the NIV translates as you've quoted.

No it doesn't. NIV has "a root", not "the root."
I cannot find a translation that has the exact text quoted.

 

[legg]

On Mon, 23 May 2005 15:28:42 -0400, Mike Monett <no@spam.com> wrote:

This could be made real cheap. Anyone know a source for inexpensive 50A
or 100A scr's?

The only SCRs specifically designed for a hard DC output crowbar, that

I'm aware of, were MCR67/68/69. The latter 2 were plastic TO220 parts,
but none were inexpensive.

The method is not really effective in devices with re-entrant or
hiccoughing current limits.

Most mfrs have come to the justifiable conclusion that better
reliability and guarantee of latch can be achieved by using
small-signal devices farther back in the control circuitry. It's one
of the main reasons you see two feedback optocouplers - the second is
used to trigger a latch in the primary drive circuit.

You know the supply has latched if it has to be unplugged from the
wall for xxseconds before it will restart.

RL

 

[Mike Monett]

Pooh Bear wrote:

I have a copy ( a few yrs old ) of BSEN60065 which is pretty similar to 60950.
Note : BSEN = the adopted British standard based on the IEC original. 60950 is
specifically IT equipment whereas 60065 is listed as audio and video equipment
now IIRC.

Graham

Still pricey. BS EN 60065:2002 = $351.26 USD

http://www.techstreet.com/cgi-bin/detail?product_id=1115682

Seems awfully expensive, especially when time and travel for the committee
members are probably paid by their own companies.

So who gets the profit?

Mike Monett

 

[Mike Monett]

legg wrote:

On Mon, 23 May 2005 15:28:42 -0400, Mike Monett <no@spam.com
wrote:

This could be made real cheap. Anyone know a source for
inexpensive 50A or 100A scr's?

The only SCRs specifically designed for a hard DC output crowbar,
that I'm aware of, were MCR67/68/69. The latter 2 were plastic
TO220 parts, but none were inexpensive.

The method is not really effective in devices with re-entrant or
hiccoughing current limits.

My interest is adding ov protection to older supplies. I'd fire a
latch that crowbarred the supply voltages and removed the ac supply.
A led would indicate which voltage failed. A simple 40A npn on +12V
and +5V would probably do fine. They wouldn't even need a heatsink.

Most mfrs have come to the justifiable conclusion that better
reliability and guarantee of latch can be achieved by using
small-signal devices farther back in the control circuitry. It's
one of the main reasons you see two feedback optocouplers - the
second is used to trigger a latch in the primary drive circuit.

You know the supply has latched if it has to be unplugged from the
wall for xxseconds before it will restart.

RL

Can you suggest a simple way to test the ov protection? If I
understand correctly, most power supplies require a load to operate
properly. So if you tried activating the ov protection by connecting
an external supply to raise the voltage, the power supply may do
wierd things.

Is there any other way to see how well the ov protection works?

Mike Monett

 

[Clifford Heath]

Guy Macon wrote:

Normally I silently killfile anyone who is rude enough to hijack
a discussion about electronics

So do I. But I didn't hijack it, any more than you did.

turn it into another boring religion/politics discussion

The proposition may have a religious origin, but I don't see any
religious arguments about it here. And surely discussion about
human values (with respect to dealings in fake electronic goods)
is not off-limits? I know that in my religious days my engineering
career was definitely restricted by misinterpretation of this
injunction.

When a Bible passage is quoted, the default assumption is that
it's the King James Version.

Fair point - but the KJV is wrong now, as you and I pointed out.
I could have dragged out the Greek too, but I'm not that bloody-
minded. The Latin Vulgate doesn't even mention money - it's better
translated as "covetousness is...", which is also closer to the
Greek filarguria, avarice.

He also should have corrected the entire
quote; he got "all kinds of evil" but missed "a root."

the root/a root becomes immaterial when you include "kinds of".
Either way it's clear that *not* all evil is said to stem from it,
contrary to the way this idea has entered popular culture, and
that was what I aimed to correct.

this is a passage where the changes in english language...

Interesting point, I hadn't realised that KJV might have once been
correct here.

Can we go back to talking about electronics now?

Please...

 

[legg]

On Tue, 24 May 2005 16:21:48 -0400, Mike Monett <no@spam.com> wrote:

Can you suggest a simple way to test the ov protection? If I
understand correctly, most power supplies require a load to operate
properly. So if you tried activating the ov protection by connecting
an external supply to raise the voltage, the power supply may do
wierd things.

Is there any other way to see how well the ov protection works?

You can usually back-drive lower powered quasi-regulated auxiliaries
as you describe. The test is also partially effective in testing an
OVP circuit that is an independant thyristor crowbar. It may damage
simpler linear post-regulator circuits, however.

Some redundant devices are designed to be immune to
externally-generated faults. OVP may not be provided on some outputs.

Do not be surprised if the OVP thresholds are set higher than you
might feel comfortable with - read the spec before testing. The test
is incomplete if the unit is not demonstrated recover, on the removal
and re-application of input power.

If a main output has remote sense lines, the output voltage may be
alterable by disconnecting these and lightly loading them. This will
cause an increased output voltage on the main terminals due to current
flow in default-coupling resistive elements (usually internal 22 to
100R resistors couple the sense lines to the output lines when sense
lines are open).

Some supplies have a 'margin' terminal that can be used to alter the
output, but these may be idiot-proofed to limit the deviation made
possible.

If you have access to the regulation circuit, temporarily wiring in a
variable resistor, to parallel the shunting element in the voltage
divider, will allow the same effect as margining. Some products may
have an internal test point intended to induce an overvoltage
condition when grounded, for use in automated testing.

You can purchase fairly simple 2-terminal crowbar protection modules
that can be value-added-on. How effective these can be, on
higher-current low-voltage supplies, is questionable. OVP is intended
to prevent damage to hardware - not to protect data integrity - in the
event of a PSU single fault.

If lower-than nominal voltages also present a threat - it might be
worthwhile paying attention to how your computer handles the
power-good signal line. This is often configured to indicate
out-of-tolerance outputs, including undervoltage, but I have yet to
see a PC that uses them sensibly.

If you're really concerned about the quality of the power provided by
a PC supply, you should probably obtain devices that demonstrate the
desired quality and performance.

I've been blind-sided by simple failures in the my own PC's supply
signal lines - and power conversion is supposed to be my area of
expertise. Ignoring PSU quality really doesn't pay in the long run.

RL

 

[Mike Monett]

legg wrote:

[... for brevity]

If you're really concerned about the quality of the power provided by
a PC supply, you should probably obtain devices that demonstrate the
desired quality and performance.

I've been blind-sided by simple failures in the my own PC's supply
signal lines - and power conversion is supposed to be my area of
expertise. Ignoring PSU quality really doesn't pay in the long run.

RL

Thanks for the excellent descriptions, Rob. I definitely will take your
advise and check the ps very carefully.

Mike Monett

 

[Guy Macon]

bigcat@meeow.co.uk wrote:

Pooh Bear wrote:

They have quite long enough life to need parts to be properly rated.

'properly' isnt one single fixed number. The further away from abs max
you run it, the longer it lasts. You can run it up close to limit if
you dont need it to last 5 yaers.

....and you don't need a low probability of failure in the first year.

 

[Pooh Bear]

Guy Macon wrote:

bigcat@meeow.co.uk wrote:

Pooh Bear wrote:

They have quite long enough life to need parts to be properly rated.

'properly' isnt one single fixed number. The further away from abs max
you run it, the longer it lasts. You can run it up close to limit if
you dont need it to last 5 yaers.

...and you don't need a low probability of failure in the first year.

In my specific area of interest ppl are now expecting 3 yr warranties. Some
suppliers are offering 5 yrs.

Graham

 

[Pooh Bear]

bigcat@meeow.co.uk wrote:

Pooh Bear wrote:
Guy Macon wrote:
bigcat@meeow.co.uk wrote:

They have quite long enough life to need parts to be properly rated.

'properly' isnt one single fixed number. The further away from abs max
you run it, the longer it lasts. You can run it up close to limit if
you dont need it to last 5 yaers.

...and you don't need a low probability of failure in the first year.

In my specific area of interest ppl are now expecting 3 yr warranties. Some
suppliers are offering 5 yrs.

Yes, precisely because of the failure rate in that time.

We don't expect some of those offering 5 yr warranties to be around 5 yrs later
to honour them !

Graham